U.S. patent application number 13/518171 was filed with the patent office on 2012-10-11 for brake system.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Tetsuya Miyazaki, Takayuki Yamamoto.
Application Number | 20120256477 13/518171 |
Document ID | / |
Family ID | 44355068 |
Filed Date | 2012-10-11 |
United States Patent
Application |
20120256477 |
Kind Code |
A1 |
Miyazaki; Tetsuya ; et
al. |
October 11, 2012 |
BRAKE SYSTEM
Abstract
A brake system including: (a) a manual hydraulic pressure
source; (b) a power hydraulic pressure source; (c) a high pressure
generator for generating high pressure, by utilizing pressure of
the power hydraulic pressure source; (d) a common passage to which
first and second brake cylinders and the high pressure generator
are connected; (e) a high-pressure-generator cut-off valve disposed
between the common passage and the high pressure generator; (f) a
first manual-pressure-source passage connecting a first individual
passage and the manual hydraulic pressure source; (g) a first
manual-pressure-source cut-off valve provided in the first
manual-pressure-source passage; (h) a first valve provided between
the second brake cylinder and a connected portion of the first
individual passage which is connected to the first
manual-pressure-source passage; and (i) a pressure-supply control
device for controlling supply of pressure to the brake cylinders,
by controlling the high-pressure-generator cut-off valve, first
valve and first manual-pressure-source cut-off valve.
Inventors: |
Miyazaki; Tetsuya;
(Toyota-shi, JP) ; Yamamoto; Takayuki; (Aichi-gun,
JP) |
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
44355068 |
Appl. No.: |
13/518171 |
Filed: |
February 2, 2010 |
PCT Filed: |
February 2, 2010 |
PCT NO: |
PCT/JP2010/051404 |
371 Date: |
June 21, 2012 |
Current U.S.
Class: |
303/6.01 |
Current CPC
Class: |
B60T 8/885 20130101;
B60T 13/165 20130101; B60T 2270/402 20130101; B60T 13/168 20130101;
B60T 8/94 20130101; B60T 8/4081 20130101 |
Class at
Publication: |
303/6.01 |
International
Class: |
B60T 13/128 20060101
B60T013/128; B60T 13/16 20060101 B60T013/16 |
Claims
1. A brake system comprising: a plurality of hydraulic brakes
provided for respective wheels of a vehicle, and configured to be
activated by hydraulic pressures of respective brake cylinders
thereof so as to restrain rotations of the respective wheels; a
manual hydraulic pressure source which is configured to generate
hydraulic pressure by operation of a brake operating member by an
operator; a power hydraulic pressure source which is configured to
generate hydraulic pressure by supply of electric energy thereto; a
high pressure generator which is configured to generate hydraulic
pressure that is higher than the hydraulic pressure of said manual
hydraulic pressure source, by utilizing the hydraulic pressure of
said power hydraulic pressure source; a common passage to which a
first brake cylinder, a second brake cylinder and said high
pressure generator are connected, said first brake cylinder being
one of said brake cylinders of said hydraulic brakes and being
connected to said common passage via a first individual passage,
said second brake cylinder being one of said brake cylinders that
is other than said first brake cylinder and being connected to said
common passage via a second individual passage that is other than
said first individual passage; a high-pressure-generator cut-off
valve disposed between said common passage and said high pressure
generator; a first manual-pressure-source passage connecting said
first individual passage and said manual hydraulic pressure source;
a first manual-pressure-source cut-off valve provided in said first
manual-pressure-source passage; a first valve provided in a portion
of a pressure supply passage which is located between a connected
portion of said pressure supply passage and said second brake
cylinder, said pressure supply passage including said first
individual passage, second individual passage and common passage,
said pressure supply passage being connected at said connected
portion thereof to said first manual-pressure-source passage; and a
pressure-supply control device configured to control supply of the
hydraulic pressure to each of said first and second brake
cylinders, by controlling at least said high-pressure-generator
cut-off valve, first valve and first manual-pressure-source cut-off
valve.
2. The brake system according to claim 1, wherein said
pressure-supply control device includes an electromagnetic-valve
controlling portion configured to control said
high-pressure-generator cut-off valve, first valve and first
manual-pressure-source cut-off valve, so as to establish a first
state and a second state, such that the hydraulic pressure of said
high pressure generator is supplied to said first brake cylinder
and second brake cylinder by placing said high-pressure-generator
cut-off valve and first valve first valve in open states and
placing said first manual-pressure-source cut-off valve in a closed
state when said first state is established, and such that the
hydraulic pressure of said manual hydraulic pressure source is
supplied to said first brake cylinder with said first brake
cylinder being isolated from said high pressure generator and said
second brake cylinder by placing said high-pressure-generator
cut-off valve and first valve in closed states and placing said
first manual-pressure-source cut-off valve in an open state.
3. The brake system according to claim 1, wherein each of said
high-pressure-generator cut-off valve and said first valve is
constituted by a normally-open electromagnetic valve that is to be
placed in an open state when electric current is not being supplied
to a solenoid thereof, and wherein said first
manual-pressure-source cut-off valve is constituted by a
normally-closed electromagnetic valve that is to be placed in a
closed state when electric current is not being supplied to a
solenoid thereof.
4. The brake system according to claim 1, comprising first and
second manual hydraulic pressure sources and a second
manual-pressure-source cut-off valve, wherein said first valve is
provided in a portion of said pressure supply passage which is
located between a high-pressure-generator connected portion of said
pressure supply passage and said second brake cylinder, said
pressure supply passage being connected at said
high-pressure-generator connected portion thereof to said high
pressure generator, wherein said first manual hydraulic pressure
source is connected to said first brake cylinder via said first
manual-pressure-source passage, while said second manual hydraulic
pressure source is connected to said second brake cylinder via a
second manual-pressure-source passage that is other than said first
manual-pressure-source passage, and wherein said second
manual-pressure-source cut-off valve is provided in said second
manual-pressure-source passage.
5. The brake system according to claim 1, comprising first and
second manual hydraulic pressure sources, wherein said first manual
hydraulic pressure source is connected to said first brake cylinder
via said first manual-pressure-source passage, wherein said second
manual hydraulic pressure source is connected to said second brake
cylinder via a second manual-pressure-source passage that is other
than said first manual-pressure-source passage, wherein said first
valve is provided in a portion of said pressure supply passage
which is located between said connected portion of said pressure
supply passage and a high-pressure-generator connected portion of
said pressure supply passage, said pressure supply passage being
connected at said high-pressure-generator connected portion thereof
to said high pressure generator, said brake system comprising: a
second manual-pressure-source cut-off valve provided in said second
manual-pressure-source passage; and a second valve provided in a
portion of said pressure supply passage which is located between
said high-pressure-generator connected portion of said pressure
supply passage and a second-manual-pressure-source-passage
connected portion of said pressure supply passage, said pressure
supply passage being connected at said
second-manual-pressure-source-passage connected portion thereof to
said second manual-pressure-source passage.
6. The brake system according to claim 5, wherein said second valve
is constituted by a normally-closed electromagnetic valve that is
to be placed in a closed state when electric current is not being
supplied to a solenoid thereof, and wherein said second
manual-pressure-source cut-off valve is constituted by a
normally-open electromagnetic valve that is to be placed in an open
state when electric current is not being supplied to a solenoid
thereof.
7. The brake system according to claim 5, wherein said hydraulic
brakes are provided for respective front right, front left, rear
right and rear left wheels of the vehicle that constitute two pairs
of wheels, each pair of the two pairs of wheels being constituted
by two of the wheels located in respective positions that are
diagonal to each other, wherein said brake cylinders of said
hydraulic brakes are connected to said common passage via
respective individual passages, wherein each of two of said
individual passages, which are connected to respective two of said
brake cylinders provided for respective two of the wheels that
constitute one pair of the two pairs of wheels, is provided with a
pressure-increasing control valve constituted by a normally-open
electromagnetic valve that is to be placed in an open state when
electric current is not being supplied to a solenoid thereof, and
wherein each of two of said individual passages, which are
connected to respective two of said brake cylinders provided for
respective two of the wheels that constitute another one pair of
the two pairs of wheels, is provided with a pressure-increasing
control valve constituted by a normally-closed electromagnetic
valve that is to be placed in a closed state when electric current
is not being supplied to a solenoid thereof.
8. The brake system according to claim 1, wherein said hydraulic
brakes are provided for respective front right, front left, rear
right and rear left wheels of the vehicle, and wherein said brake
cylinders of ones of said hydraulic brakes which are provided for
the rear right and left wheels are connected to said common passage
via a third individual passage, said brake system comprising a
third valve which is provided in said third individual passage and
which is constituted by a normally-closed electromagnetic valve
that is to be placed in a closed state when electric current is not
being supplied to a solenoid thereof.
9. The brake system according to claim 8, comprising a
rear-wheel-brake-cylinder-side check valve which is provided in
parallel with said third valve, wherein said
rear-wheel-brake-cylinder-side check valve is configured to allow
flow of a working fluid in a direction toward said common passage
away from said brake cylinders of said ones of said hydraulic
brakes which are provided for the rear right and left wheels, and
to inhibit flow of the working fluid in a direction opposite to
said direction toward said common passage away from said ones of
said brake cylinders.
10. The brake system according to claim 1, wherein said power
hydraulic pressure source is connected to said common passage via a
passage bypassing said high pressure generator, said brake system
comprising an output hydraulic pressure control device configured
to control the hydraulic pressure outputted by said power hydraulic
pressure source.
11. The brake system according to claim 1, wherein said high
pressure generator is disposed among said first brake cylinder,
said second brake cylinder, said power hydraulic pressure source
and said manual hydraulic pressure source, and wherein said high
pressure generator is to be activated mechanically by the hydraulic
pressure of said manual hydraulic pressure source.
12. The brake system according to claim 11, wherein said high
pressure generator includes (a) a mechanical pressure-increasing
device configured to increase the hydraulic pressure of said manual
hydraulic pressure source and to output the increased hydraulic
pressure and (b) a high-pressure-side check valve disposed between
said mechanical pressure-increasing device and said power hydraulic
pressure source, and wherein said high-pressure-side check valve is
configured to allow flow of a working fluid in a direction toward
said mechanical pressure-increasing device away from said power
hydraulic pressure source, and to inhibit flow of the working fluid
in a direction opposite to said direction toward said mechanical
pressure-increasing device away from said power hydraulic pressure
source.
13. The brake system according to claim 12, wherein said mechanical
pressure-increasing device includes (a) a housing, (b) a stepped
piston which is fluid-tightly and slidably fitted in said housing
and which has a large diameter portion and a small diameter
portion, (c) a large diameter chamber which is located on a side of
said large diameter portion of said stepped piston and which is
connected to said manual hydraulic pressure source, (d) a small
diameter chamber which is located on a side of said small diameter
portion of said stepped piston and which is connected to said brake
cylinders, (e) a high pressure chamber to which said power
hydraulic pressure source is connected, and (f) a high-pressure
supply valve which is disposed between said high pressure chamber
and said small diameter chamber and which is to be switched from a
closed state to an open state by forward movement of said stepped
piston, wherein said high-pressure-side check valve is disposed
between said high pressure chamber and said power hydraulic
pressure source, and wherein said high-pressure-side check valve is
configured to allow flow of a working fluid in a direction toward
said high pressure chamber away from said power hydraulic pressure
source, and to inhibit flow of the working fluid in a direction
opposite to said direction toward said high pressure chamber away
from said power hydraulic pressure source.
14. The brake system according to claim 13, wherein said high
pressure generator includes a manual-side check valve disposed
between said manual hydraulic pressure source and an output side
portion of said mechanical pressure-increasing device, and wherein
said manual-side check valve is configured to allow flow of the
working fluid in a direction toward said mechanical
pressure-increasing device away from said manual hydraulic pressure
source, and to inhibit flow of the working fluid in a direction
opposite to said direction toward said mechanical
pressure-increasing device away from said manual hydraulic pressure
source.
15. The brake system according to claim 1, wherein said
high-pressure-generator cut-off valve is constituted by a
normally-open electromagnetic valve that is to be placed in an open
state when electric current is not being supplied to a solenoid
thereof.
16. The brake system according to claim 1, wherein said power
hydraulic pressure source includes a pump device and an accumulator
that is configured to store therein a working fluid discharged from
said pump device.
17. The brake system according to claim 1, wherein said power
hydraulic pressure source is connected to said common passage via a
passage bypassing said high pressure generator, said brake system
comprising an output hydraulic pressure control device configured
to control the hydraulic pressure outputted by said power hydraulic
pressure source, wherein said pressure-supply control device
includes an electromagnetic-valve controlling portion that is
configured to place said high-pressure-generator cut-off valve,
first valve and first manual-pressure-source cut-off valve in a
closed state, an open state and a closed state, respectively, and
to cause the hydraulic pressure controlled by said output hydraulic
pressure control device to be supplied to said common passage in a
state in which said common passage is isolated from said high
pressure generator while said first brake cylinder is isolated from
said manual hydraulic pressure source.
18. The brake system according to claim 1, comprising: a
fluid-leakage possibility detecting device configured to detect
presence of possibility of fluid leakage in said brake system; and
an electromagnetic-valve controlling portion configured to place at
least said first valve in a closed state when the presence of
possibility of fluid leakage is detected by said fluid-leakage
possibility detecting device.
19. The brake system according to claim 1, wherein said high
pressure generator is disposed among said first brake cylinder,
said second brake cylinder, said power hydraulic pressure source
and said manual hydraulic pressure source, and wherein said high
pressure generator is to be activated mechanically by the hydraulic
pressure of said manual hydraulic pressure source that is
constituted by a pressurized chamber of said master cylinder.
Description
TECHNICAL FIELD
[0001] The present invention relates to a brake system having a
hydraulic brake configured to restrain rotation of a wheel.
BACKGROUND ART
[0002] Patent Document 1 discloses a brake system having (a) a
hydraulic brake configured to restrain rotation of a wheel, (b) a
master cylinder, (c) an accumulator, (d) a pressure increasing
mechanism utilizing hydraulic pressure of the accumulator and
activatable by activation of an electric actuator, and (e) a
selector valve configured to select a higher one of hydraulic
pressure of the pressure increasing mechanism and hydraulic
pressure of the master cylinder, and to supply the selected
hydraulic pressure to a brake cylinder of the hydraulic brake.
[0003] When the electric actuator is normal, the pressure
increasing mechanism is activated by the electric actuator. When
the electric actuator is in failure, the pressure increasing
mechanism is activated by the hydraulic pressure of the master
cylinder. Further, when the working fluid of high pressure can be
supplied from the accumulator, the pressure increasing mechanism
can generate hydraulic pressure that is higher than the hydraulic
pressure of the master cylinder. When the working fluid of the
accumulator becomes low, the hydraulic pressure outputted by the
pressure increasing mechanism becomes low, too.
[0004] Since the higher one of the hydraulic pressure of the
pressure increasing mechanism and the hydraulic pressure of the
master cylinder is selected by the selector valve so as to be
supplied to the brake cylinder, the hydraulic pressure of the
master cylinder is supplied to the brake cylinder when the
hydraulic pressure of the accumulator is low, namely, when the
hydraulic pressure outputted by the pressure increasing mechanism
is low.
[0005] Patent Document 2 discloses a brake system having (a)
hydraulic brakes provided for front right, front left, rear right
and rear left wheels of a vehicle and configured to restrain
rotations of the wheels, (b) a master cylinder, (c) a mechanical
booster mechanism provided between the master cylinder and brakes
cylinders of ones of the hydraulic brakes which are provided for
the front right and front left wheels, (d) a high pressure source
pressure of the high pressure source. In this brake system, when
the high pressure source and the electromagnetic valve are normal,
the hydraulic pressure of the high pressure source controlled by
the electromagnetic valve is supplied to the brake cylinders
provided for the front and rear wheels. When components such as the
electromagnetic valve are in failure, the hydraulic pressure
generated by the mechanical pressure increasing mechanism is
supplied to the brake cylinders provided for the front wheel while
the hydraulic pressure of the master cylinder is supplied to the
brake cylinders provided for the rear wheels.
PRIOR ART DOCUMENTS
Patent Documents
[0006] [Patent Document 1] JP-2009-502645A [0007] [Patent Document
2] JP-H10-287227A
DISCLOSURE OF THE INVENTION
Object to be Achieved by the Invention
[0008] An object of the present invention is to improve a brake
system.
Measures for Achieving the Object and Effect
[0009] A brake system described in claim 1 includes: (a) a
plurality of hydraulic brakes provided for respective wheels of a
vehicle, and configured to be activated by hydraulic pressures of
respective brake cylinders thereof so as to restrain rotations of
the respective wheels; (b) a manual hydraulic pressure source which
is configured to generate hydraulic pressure by operation of a
brake operating member by an operator; (c) a power hydraulic
pressure source which is configured to generate hydraulic pressure
by supply of electric energy thereto; (d) a high pressure generator
which is configured to generate hydraulic pressure that is higher
than the hydraulic pressure of said manual hydraulic pressure
source, by utilizing the hydraulic pressure of said power hydraulic
pressure source; (e) a common passage to which a first brake
cylinder, a second brake cylinder and said high pressure generator
are connected, said first brake cylinder being one of said brake
cylinders of said hydraulic brakes and being connected to said
common passage via a first individual passage, said second brake
cylinder being one of said brake cylinders that is other than said
first brake cylinder and being connected to said common passage via
a second individual passage that is other than said first
individual passage; (f) a high-pressure-generator cut-off valve
disposed between said common passage and said high pressure
generator; (g) a first manual-pressure-source passage connecting
said first individual passage and said manual hydraulic pressure
source; (h) a first manual-pressure-source cut-off valve provided
in said first manual-pressure-source passage; (i) a first valve
provided in a portion of a pressure supply passage which is located
between a connected portion of said pressure supply passage and
said second brake cylinder, said pressure supply passage including
said first individual passage, second individual passage and common
passage, said pressure supply passage being connected at said
connected portion thereof to said first manual-pressure-source
passage; and (j) a pressure-supply control device configured to
control supply of the hydraulic pressure to each of said brake
cylinders, by controlling at least said high-pressure-generator
cut-off valve, first valve and first manual-pressure-source cut-off
valve.
[0010] In the present brake system, for example, when the
high-pressure-generator cut-off valve and the first valve are
placed in open states, the hydraulic pressure of the high pressure
generator can be supplied to the first and second brake cylinders.
When the first manual-pressure-source cut-off valve is placed in a
closed state with the high-pressure-generator cut-off valve and the
first valve being placed in the open states, it is possible to
prevent the hydraulic pressure of the first brake cylinder from
flowing back to the manual hydraulic pressure source.
[0011] Further, when the first manual-pressure-source cut-off valve
is placed in an open state with the high-pressure-generator cut-off
valve and the first valve being placed in closed states, it is
possible to allow the first brake cylinder to be in communication
with the master cylinder while isolating the first brake cylinder
from the high pressure generator and the second brake cylinder.
Thus, the first and second brake cylinders are isolated from each
other, so that, even in the event of fluid leakage occurring in one
of a brake line including the first brake cylinder and another
brake line including the second brake cylinder, it is possible to
avoid the other of the brake lines from being influenced by the
fluid leakage occurring in the one of the brake lines.
[0012] Thus, in the present brake system, by controlling the
high-pressure-generator cut-off valve, first valve and hitting
first manual-pressure-source cut-off valve, the hydraulic pressure
can be supplied to each of the brake cylinders in accordance with
various modes.
[0013] The first valve may be disposed in a portion of the pressure
supply passage which portion is located between the second brake
cylinder and a high-pressure-generator connected portion of the
pressure supply passage at which the pressure supply passage is
connected to the high pressure generator, or alternatively, may be
disposed in another portion of the pressure supply passage which
portion is located between the first brake cylinder and the
high-pressure-generator connected portion of the pressure supply
passage (i.e., which is located between the high-pressure-generator
connected portion of the pressure supply passage and the
above-described connected portion of the pressure supply passage at
which the pressure supply passage is connected to the first
manual-pressure-source passage). Irrespective of whether the first
valve is disposed in the above-described portion or another portion
of the pressure supply passage, it is possible to selectively
communicate and isolate the first and second brake cylinders to and
from each other.
VARIOUS MODES OF THE INVENTION
[0014] There will be described various modes of the invention
deemed to contain claimable features for which protection is
sought. Hereinafter, the invention deemed to contain the claimable
features will be referred to as "claimable invention" where
appropriate. The claimable invention includes at least "the present
invention" or "the invention of the present application" which is
an invention described in claims, and could include also specific
concept of the invention of the present application, generic
concept of the invention of the present application and other
concept of the invention of the present application. Each of these
modes of the invention is numbered like the appended claims and
depends from the other mode or modes, where appropriate, for easier
understanding of the technical features disclosed in the present
specification. It is to be understood that the claimable invention
is not limited to the technical features or any combinations
thereof which will be described in each of these modes. That is,
the scope of the claimable invention should be interpreted in the
light of the following descriptions accompanying the various modes
and preferred embodiments of the invention. In a limit in
accordance with such an interpretation, a mode of the claimable
invention can be constituted by not only each one of these modes
but also either a mode provided by any one of these modes and
additional components incorporated therein or a mode provided by
any one of these modes without some of components recited
therein.
[0015] (1) A brake system, characterized by comprising:
[0016] a plurality of hydraulic brakes provided for respective
wheels of a vehicle, and configured to be activated by hydraulic
pressures of respective brake cylinders thereof so as to restrain
rotations of the respective wheels;
[0017] a manual hydraulic pressure source which is configured to
generate hydraulic pressure by operation of a brake operating
member by an operator;
[0018] a power hydraulic pressure source which is configured to
generate hydraulic pressure by supply of electric energy
thereto;
[0019] a high pressure generator which is configured to generate
hydraulic pressure that is higher than the hydraulic pressure of
said manual hydraulic pressure source, by utilizing the hydraulic
pressure of said power hydraulic pressure source;
[0020] a common passage to which a first brake cylinder, a second
brake cylinder and said high pressure generator are connected, said
first brake cylinder being one of said brake cylinders of said
hydraulic brakes and being connected to said common passage via a
first individual passage, said second brake cylinder being one of
said brake cylinders that is other than said first brake cylinder
and being connected to said common passage via a second individual
passage that is other than said first individual passage;
[0021] a high-pressure-generator cut-off valve disposed between
said common passage and said high pressure generator;
[0022] a first manual-pressure-source passage connecting said first
individual passage and said manual hydraulic pressure source;
[0023] a first manual-pressure-source cut-off valve provided in
said first manual-pressure-source passage;
[0024] a first valve provided in a portion of a pressure supply
passage which is located between a connected portion of said
pressure supply passage and said second brake cylinder, said
pressure supply passage including said first individual passage,
second individual passage and common passage, said pressure supply
passage being connected at said connected portion thereof to said
first manual-pressure-source passage; and
[0025] a pressure-supply control device configured to control
supply of the hydraulic pressure to each of said brake cylinders,
by controlling at least said high-pressure-generator cut-off valve,
first valve and first manual-pressure-source cut-off valve.
[0026] The high pressure generator, which is configured to generate
hydraulic pressure that is higher than the hydraulic pressure of
the manual hydraulic pressure source, may be activated either
mechanically or by supply of electric energy thereto. Further, the
high pressure generator may include at least one of components of
the power hydraulic pressure source or may be constituted by a
pressure increasing mechanism (such as boosting mechanism)
configured to increase hydraulic pressure of a manual hydraulic
pressure source that is other than the power hydraulic pressure
source. The pressure increasing mechanism may be provided either
integrally with the manual hydraulic pressure source or
independently of the manual hydraulic pressure source.
[0027] Further, each of the high-pressure-generator cut-off valve,
first valve and first manual-pressure-source cut-off valve may be
either a normally-open electromagnetic valve that is to be placed
in an open state when electric current is not being supplied to a
solenoid thereof or a normally-closed electromagnetic valve that is
to be placed in a closed state when electric current is not being
supplied to the solenoid thereof.
[0028] The electromagnetic valve is a valve that is controllable to
be placed in at least the open and closed states by controlling
electric current supplied to the solenoid of the valve. The
electromagnetic valve may be either a linear control valve or a
simple on/off valve. In the linear control valve, a difference
between the hydraulic pressure on one of opposite sides of the
valve and the hydraulic pressure on the other of the opposite sides
of the valve or/and an opening angle of the valve are continuously
controllable by continuously controlling the electric current
supplied to the solenoid of the valve. In the simple on/off valve,
the open and closed states can be selectively established by
selectively turning ON/OFF the supply of the electric current to
the solenoid of the valve. Hereinafter, in the description of the
present application, the term "electromagnetic valve" may be
interpreted as either a linear control valve or a simple on/off
valve, unless otherwise specified.
[0029] (2) The brake system according to mode (1), wherein said
pressure-supply control device includes an electromagnetic-valve
controlling portion configured to control said
high-pressure-generator cut-off valve, first valve and first
manual-pressure-source cut-off valve, so as to establish a first
state and a second state, such that the hydraulic pressure of said
high pressure generator is supplied to said first brake cylinder
and second brake cylinder by placing said high-pressure-generator
cut-off valve and first valve first valve in open states and
placing said first manual-pressure-source cut-off valve in a closed
state when said first state is established, and such that the
hydraulic pressure of said manual hydraulic pressure source is
supplied to said first brake cylinder with said first brake
cylinder being isolated from said high pressure generator and said
second brake cylinder by placing said high-pressure-generator
cut-off valve and first valve in closed states and placing said
first manual-pressure-source cut-off valve in an open state.
[0030] (3) The brake system according to mode (1) or (2), wherein
each of said high-pressure-generator cut-off valve and said first
valve is constituted by a normally-open electromagnetic valve that
is to be placed in an open state when electric current is not being
supplied to a solenoid thereof.
[0031] For example, (a) where the higher pressure generator is
capable of generating the hydraulic pressure higher than the
hydraulic pressure of the manual hydraulic pressure source even
without supply of electric energy thereto, or (b) where the high
pressure generator is capable of generating the hydraulic pressure
higher than the hydraulic pressure of the manual hydraulic pressure
source owing to electric energy that can be supplied thereto from
an auxiliary electric line in case of failure of a control system
or failure of a main electric line, it is possible to supply the
hydraulic pressure higher than the hydraulic pressure of the manual
hydraulic pressure source, to both of the first and second brake
cylinders in the case of the failure of the main electric line when
the above-described first state is being established.
[0032] The brake system disclosed in Patent Document 2 is different
from the brake system described in this mode, because valves
(electromagnetic valves 80-88) each corresponding to the first
valve is a normally-closed electromagnetic valve in the brake
system of Patent Document 2.
[0033] (4) The brake system according to any one of modes (1)-(3),
wherein said first manual-pressure-source cut-off valve is
constituted by a normally-closed electromagnetic valve that is to
be placed in a closed state when electric current is not being
supplied to a solenoid thereof.
[0034] For example, where the hydraulic pressure of the high
pressure generator is supplied to the first and second brake
cylinders in case of failure of the electric system, it is possible
to prevent the working fluid from flowing back to the manual
hydraulic pressure source from the first and second brake
cylinders, since the first manual-pressure-source cut-off valve is
placed in the closed state.
[0035] The brake system disclosed in Patent Document 2 is different
from the brake system described in this mode, because
master-cylinder cut-off valves (valves 30, 40, 46, 56) each
corresponding to the manual-pressure-source cut-off valve is a
normally-open electromagnetic valve in the brake system of Patent
Document 2.
[0036] (5) The brake system according to any one of modes (1)-(4),
comprising first and second manual hydraulic pressure sources and a
second manual-pressure-source cut-off valve,
[0037] wherein said first valve is provided in a portion of said
pressure supply passage which is located between a
high-pressure-generator connected portion of said pressure supply
passage and said second brake cylinder, said pressure supply
passage being connected at said high-pressure-generator connected
portion thereof to said high pressure generator,
[0038] wherein said first manual hydraulic pressure source is
connected to said first brake cylinder via said first
manual-pressure-source passage, while said second manual hydraulic
pressure source is connected to said second brake cylinder via a
second manual-pressure-source passage that is other than said first
manual-pressure-source passage,
[0039] and wherein said second manual-pressure-source cut-off valve
is provided in said second manual-pressure-source passage.
[0040] The first and second manual hydraulic pressure sources may
be constituted by, for example, two pressurizing chambers (i.e.,
first and second pressurizing chambers) of a tandem master
cylinder.
[0041] For example, by placing the first valve and the
high-pressure-generator cut-off valve in the closed states while
placing the first and second manual-pressure-source cut-off valves
in the open states, it is possible to supply the hydraulic
pressures of the manual hydraulic pressure sources to the first and
second brake cylinders with the first and second brake cylinders
being isolated from each other.
[0042] Further, by placing the first valve and the
high-pressure-generator cut-off valve in the open states while
placing the first and second manual-pressure-source cut-off valves
in the closed states, it is possible to supply the hydraulic
pressure of the high pressure generator to the first and second
brake cylinders with the first and second brake cylinders being
isolated from the manual hydraulic pressure sources.
[0043] The second manual-pressure-source passage is connected to a
portion of the pressure supply passage which portion is located
between the first valve and the second brake cylinder, without via
the common passage.
[0044] (6) The brake system according to mode (5), wherein said
second manual-pressure-source cut-off valve is constituted by a
normally-open electromagnetic valve that is to be placed in an open
state when electric current is not being supplied to a solenoid
thereof.
[0045] Even in event of failure of the electric system, the
hydraulic pressure of the manual hydraulic pressure source can be
reliably supplied to the second brake cylinder.
[0046] For example, where the high pressure generator is
constituted by a pressure increasing mechanism that is to be
activated by the hydraulic pressure of the first pressurizing
chamber of the master cylinder so as to increase the hydraulic
pressure of the first pressurizing chamber, the hydraulic pressure
of the pressure increasing mechanism is supplied to the first and
second brake cylinders and also to the second pressurizing chamber
of the master cylinder whereby the hydraulic pressure outputted
from the first pressurizing chamber is increased, when the first
manual-pressure-source cut-off valve is placed in the closed state
while the first valve and the second manual-pressure-source cut-off
valve are placed in the open states. Consequently, the hydraulic
pressure supplied to the pressure increasing mechanism is increased
and accordingly the hydraulic pressure outputted from the pressure
increasing mechanism is also increased whereby the hydraulic
pressure supplied to the first and second brake cylinders is also
increased.
[0047] Further, when the pressure increasing mechanism becomes
unable of increasing the hydraulic pressure of the first
pressurizing chamber, the hydraulic pressure is supplied to the
first brake cylinder from the first pressurizing chamber via the
pressure increasing mechanism while the hydraulic pressure is
supplied to the second brake cylinder from the second pressurizing
chamber. Thus, to each of the first and second brake cylinders, the
hydraulic pressure can be supplied from a corresponding one of
pressurizing chambers of the master cylinder which are other than
each other.
[0048] (7) The brake system according to any one of modes (1)-(4),
comprising first and second manual hydraulic pressure sources,
[0049] wherein said first manual hydraulic pressure source is
connected to said first brake cylinder via said first
manual-pressure-source passage,
[0050] wherein said second manual hydraulic pressure source is,
connected to said second brake cylinder via a second
manual-pressure-source passage that is other than said first
manual-pressure-source passage,
[0051] wherein said first valve is provided in a portion of said
pressure supply passage which is located between said connected
portion of said pressure supply passage and a
high-pressure-generator connected portion of said pressure supply
passage, said pressure supply passage being connected at said
high-pressure-generator connected portion thereof to said high
pressure generator,
[0052] said brake system comprising:
[0053] a second manual-pressure-source cut-off valve provided in
said second manual-pressure-source passage; and
[0054] a second valve provided in a portion of said pressure supply
passage which is located between said high-pressure-generator
connected portion of said pressure supply passage and a
second-manual-pressure-source-passage connected portion of said
pressure supply passage, said pressure supply passage being
connected at said second-manual-pressure-source-passage connected
portion thereof to said second manual-pressure-source passage.
[0055] Each of the first and second brake cylinders is provided
with a corresponding one of the first and second valves and a
corresponding one of the first and second manual-pressure-source
cut-off valves, so that it is possible to supply the hydraulic
pressure to each of the first and second brake cylinders from the
high pressure generator or the corresponding manual hydraulic
pressure, by controlling the first and second valves and the first
and second manual-pressure-source cut-off valves.
[0056] Further, it is possible to selectively communicate and
isolate the first and second brake cylinders to and from each
other.
[0057] Moreover, since the hydraulic pressures are supplied to the
first and second brake cylinders from the respective manual
hydraulic pressure sources that are other than each other, the
hydraulic pressures of the manual hydraulic pressure sources can be
reliably supplied to the manual hydraulic pressure sources.
[0058] It is noted that the first and second brake cylinders may be
brake cylinders of hydraulic brakes provided for front left and
right wheels of the vehicle.
[0059] (8) The brake system according to mode (7),
[0060] wherein said second valve is constituted by a
normally-closed electromagnetic valve that is to be placed in a
closed state when electric current is not being supplied to a
solenoid thereof,
[0061] and wherein said second manual-pressure-source cut-off valve
is constituted by a normally-open electromagnetic valve that is to
be placed in an open state when electric current is not being
supplied to a solenoid thereof.
[0062] In event of failure of the electric system, the hydraulic
pressure can be supplied to the second brake cylinder from the
second manual hydraulic pressure source, with the second brake
cylinder being isolated from the first brake cylinder and the high
pressure generator.
[0063] The first and second valves can be provided in respective
individual passages that are connected to the respective first and
second brake cylinders, so that the first and second valves serve
as pressure-increasing control valves capable of controlling the
hydraulic pressures in the respective first and second brake
cylinders.
[0064] (9) The brake system according to mode (7) or (8),
[0065] wherein said hydraulic brakes are provided for respective
front right, front left, rear right and rear left wheels of the
vehicle that constitute two pairs of wheels, each pair of the two
pairs of wheels being constituted by two of the wheels located in
respective positions that are diagonal to each other,
[0066] wherein said brake cylinders of said hydraulic brakes are
connected to said common passage via respective individual
passages,
[0067] wherein each of two of said individual passages, which are
connected to respective two of said brake cylinders provided for
respective two of the wheels that constitute one pair of the two
pairs of wheels, is provided with a pressure-increasing control
valve constituted by a normally-open electromagnetic valve that is
to be placed in an open state when electric current is not being
supplied to a solenoid thereof,
[0068] and wherein each of two of said individual passages, which
are connected to respective two of said brake cylinders provided
for respective two of the wheels that constitute another one pair
of the two pairs of wheels, is provided with a pressure-increasing
control valve constituted by a normally-closed electromagnetic
valve that is to be placed in a closed state when electric current
is not being supplied to a solenoid thereof.
[0069] When the electric current is not supplied to the solenoid of
any one of the electromagnetic valves, the two brake cylinders
provided for respective two of the wheels that constitute the
above-described one pair of wheels are in communication with the
common passage, while the two brake cylinders provided for
respective two of the wheels that constitute the above-described
another one pair of wheels are isolated from the common passage.
Therefore, the hydraulic pressure of the high pressure generator is
supplied to the two brake cylinders which are held in communication
with the common passage and which are provided for the respective
wheels located in respective positions that are diagonal to each
other, thereby making it possible to restrain generation of a yaw
moment.
[0070] Further, when the working fluid cannot be supplied at a high
rate from the high pressure generator, it is preferable that the
working fluid is supplied to two brake cylinders, namely, it is
preferable that the working fluid is not supplied to three or more
brake cylinders.
[0071] Moreover, it is common that a pressure receiving area of a
piston of the brake cylinder for the front wheel is larger than a
pressure receiving area of a piston of the brake cylinder for the
rear wheel. Therefore, when the hydraulic pressure in the
front-wheel brake cylinder and the hydraulic pressure in the
rear-wheel brake cylinder are to be equalized to each other, the
working fluid is consumed more in the front-wheel brake cylinder
than in the rear-wheel brake cylinder. In view of this, there is an
advantage that a relatively small amount of the working fluid is
required in the arrangement in which the hydraulic pressure of the
high pressure generator is supplied to a brake cylinder provided
for one of front wheels and a brake cylinder provided for one of
rear wheels, as compared with an arrangement in which the hydraulic
pressure of the high pressure generator is supplied to brake
cylinders provided for front right and left wheels.
[0072] It can be considered that the normally-open
pressure-increasing control valve provided for one of the front
right and left wheels corresponds to the first valve and that the
normally-closed pressure-increasing control valve provided for
another one of the front right and left wheels corresponds to the
second valve.
[0073] (10) The brake system according to mode (9), comprising:
[0074] a low pressure source; and
[0075] a pressure-reducing control valve disposed between said low
pressure source and one of said brake cylinders that is provided
for the rear right wheel or rear left wheel,
[0076] wherein said one of said brake cylinders is connected to one
of said individual passages which is provided with said
pressure-increasing control valve constituted by said
normally-closed electromagnetic valve,
[0077] and wherein said pressure-reducing control valve is
constituted by a normally-open electromagnetic valve that is to be
placed in an open state when electric current is not being supplied
to a solenoid thereof.
[0078] Even in the arrangement in which the pressure-increasing
control valve is constituted by a normally-closed electromagnetic
valve, it is possible to prevent brake dragging upon release of a
brake operation, because the brake cylinder is in communication
with the low pressure source.
[0079] (11) The brake system according to mode (9), comprising a
check valve disposed in parallel with said pressure-increasing
control valve that is constituted by said normally-closed
electromagnetic valve,
[0080] wherein said check valve is configured to allow flow of a
working fluid in a direction toward said common passage away from
one of said brake cylinders that is connected to said
pressure-increasing control valve constituted by said
normally-closed electromagnetic valve, and to inhibit flow of the
working fluid in a direction opposite to said direction toward said
common passage away from said one of said brake cylinders that is
connected to said pressure-increasing control valve constituted by
said normally-closed electromagnetic valve.
[0081] Since the pressure-increasing control valve is constituted
by the normally-closed electromagnetic valve, there is a risk of
brake dragging if the working fluid remains in the brake cylinder
upon release of a brake operation. However, the disposition of the
above-described check valve in parallel with the
pressure-increasing control valve enables the working fluid to flow
back to the common passage upon release of the brake operation. For
example, when the high pressure generator is in communication with
the manual hydraulic pressure source, the working fluid having
flowed back to the common passage can be returned to the manual
hydraulic pressure source via the high pressure generator, whereby
brake dragging can be prevented. Thus, where the check valve is
provided in parallel with the normally-close pressure-increasing
control valve, the pressure-reducing control valve can be
constituted by the normally-closed electromagnetic valve, thereby
making it possible to reduce consumption of the electric power.
[0082] (12) The brake system according to any one of modes
(1)-(8),
[0083] wherein said hydraulic brakes are provided for respective
front right, front left, rear right and rear left wheels of the
vehicle,
[0084] and wherein said brake cylinders of ones of said hydraulic
brakes which are provided for the rear right and left wheels are
connected to said common passage via a third individual
passage,
[0085] said brake system comprising a third valve which is provided
in said third individual passage and which is constituted by a
normally-closed electromagnetic valve that is to be placed in a
closed state when electric current is not being supplied to a
solenoid thereof.
[0086] A large braking force can be caused to more effectively act
on an entirety of the vehicle, by supplying the hydraulic pressure
to the front-wheel brake cylinder to increase the hydraulic
pressure in the front-wheel brake cylinder to a certain level,
rather than by supplying the hydraulic pressure to the rear-wheel
brake cylinder to increase the hydraulic pressure in the rear-wheel
brake cylinder to the same certain level.
[0087] In view of this, it is preferable that the working fluid is
not supplied to the rear-wheel brake cylinder when the high
pressure generator cannot supply the working fluid at a high rate,
namely, when there is a limitation on a rate of supply of the
working fluid from the high pressure generator.
[0088] In the brake system described in this mode, the brake
cylinders provided for the rear right and left wheels are connected
to the common passage via the third individual passage, so that the
hydraulic pressures in the brake cylinders provided for the rear
right and left wheels can be commonly controlled.
[0089] It is noted that the brake cylinders provided for the rear
right and left wheels can be connected to the common passage via
respective individual passages so that the hydraulic pressures in
the respective brake cylinders can be controlled independently of
each other.
[0090] (13) The brake system according to mode (12), comprising a
rear-wheel-brake-cylinder-side check valve which is provided in
parallel with said third valve,
[0091] wherein said rear-wheel-brake-cylinder-side check valve is
configured to allow flow of a working fluid in a direction toward
said common passage away from said brake cylinders of said ones of
said hydraulic brakes which are provided for the rear right and
left wheels, and to inhibit flow of the working fluid in a
direction opposite to said direction toward said common passage
away from said ones of said brake cylinders.
[0092] (14) The brake system according to any one of modes
(1)-(13),
[0093] wherein said power hydraulic pressure source is connected to
said common passage via a passage bypassing said high pressure
generator,
[0094] said brake system comprising an output hydraulic pressure
control device configured to control the hydraulic pressure
outputted by said power hydraulic pressure source.
[0095] The output hydraulic pressure control device may be
configured to control the hydraulic pressure outputted by the power
hydraulic pressure source, by either controlling the power
hydraulic pressure source or controlling at least one
electromagnetic valve that is provided for the power hydraulic
pressure source. In either arrangement, the hydraulic pressure
supplied from the power hydraulic pressure source to the common
passage is controlled by the output hydraulic pressure control
device.
[0096] Where the power hydraulic pressure source includes a pump
device, it is possible to control the hydraulic pressure discharged
from a pump, by controlling a pump motor. Where at least one
electromagnetic valve is disposed between the power hydraulic
pressure source and the common passage, it is possible to control
the hydraulic pressure supplied to the common passage, by
controlling the at least one electromagnetic valve.
[0097] In the brake system described in this mode, the plurality of
brake cylinders as well as the power hydraulic pressure source and
the high pressure generator are connected to the common passage. It
is possible to supply the hydraulic pressure to the plurality of
brake cylinders from either one of the power hydraulic pressure
source and the high pressure generator.
[0098] Further, it is possible to supply the hydraulic pressure
from the power hydraulic pressure source to at least one of the
plurality of brake cylinders, and to supply the hydraulic pressure
from the high pressure generator and/or the manual hydraulic
pressure source to the other of the plurality of brake
cylinders.
[0099] (15) The brake system according to any one of modes
(1)-(14),
[0100] wherein said high pressure generator is disposed among said
common passage, said power hydraulic pressure source and said
manual hydraulic pressure source,
[0101] and wherein said high pressure generator is to be activated
mechanically by the hydraulic pressure of said manual hydraulic
pressure source.
[0102] In the brake system described in this mode, the high
pressure generator is provided as a component that is other than
the power hydraulic pressure source, and is to be activated
mechanically. Therefore, even in event of failure of the electric
system, for example, it is possible to generate the hydraulic
pressure higher than the hydraulic pressure of the manual hydraulic
pressure source.
[0103] (16) The brake system according to mode (15),
[0104] wherein said high pressure generator includes (a) a
mechanical pressure-increasing device configured to increase the
hydraulic pressure of said manual hydraulic pressure source and to
output the increased hydraulic pressure and (b) a
high-pressure-side check valve disposed between said mechanical
pressure-increasing device and said power hydraulic pressure
source,
[0105] and wherein said high-pressure-side check valve is
configured to allow flow of a working fluid in a direction toward
said mechanical pressure-increasing device away from said power
hydraulic pressure source, and to inhibit flow of the working fluid
in a direction opposite to said direction toward said mechanical
pressure-increasing device away from said power hydraulic pressure
source.
[0106] In the brake system described in this mode, the high
pressure generator is provided as a component that is other than
the power hydraulic pressure source, and is to be activated
mechanically. Therefore, even in event of failure of the electric
system, for example, it is possible to generate the hydraulic
pressure higher than the hydraulic pressure of the manual hydraulic
pressure source.
[0107] Further, since the high-pressure-side check valve is
disposed between the power hydraulic pressure source and the
mechanical pressure-increasing device, the flow of the working
fluid between the power hydraulic pressure source and the
mechanical pressure-increasing device is inhibited when the
hydraulic pressure of the power hydraulic pressure source is not
higher than the hydraulic pressure of the mechanical
pressure-increasing device. It is therefore possible to
satisfactorily avoid reduction of the hydraulic pressure outputted
by the mechanical pressure-increasing device.
[0108] In the brake system disclosed in Patent Document 1, the
high-pressure-side check valve is not provided in the pressure
increasing mechanism, so that there is a case in which the
hydraulic pressure outputted by the pressure increasing mechanism
becomes lower than the hydraulic pressure of the master cylinder
when the hydraulic pressure of the working fluid stored in the
accumulator is low. Further, owing to the selector valves 27, 28, a
higher one of the hydraulic pressure of the master cylinder and the
hydraulic pressure of the pressure increasing mechanism is supplied
to the brake cylinders. Thus, in the brake system disclosed in
Patent Document 1, the selector valves 27, 28 are provided so as
not to supply a hydraulic pressure lower than the hydraulic
pressure of the master cylinder, to the brake cylinders.
[0109] On the other hand, in the brake system described in this
mode, owing to the high-pressure-side check valve, it is possible
to avoid the hydraulic pressure outputted by the mechanical
pressure-increasing device, from becoming lower than the hydraulic
pressure of the manual hydraulic pressure source. Thus, the
provision of the high-pressure-side check valve eliminates
necessity of provision of valves serving as the selector valves 27,
28, thereby making it possible to reduce the number of required
components and to accordingly reduce the cost.
[0110] (17) The brake system according to mode (16), wherein said
mechanical pressure-increasing device includes (a) a housing, (b) a
stepped piston which is fluid-tightly and slidably fitted in said
housing and which has a large diameter portion and a small diameter
portion, (c) a large diameter chamber which is located on a side of
said large diameter portion of said stepped piston and which is
connected to said manual hydraulic pressure source, (d) a small
diameter chamber which is located on a side of said small diameter
portion of said stepped piston and which is connected to said brake
cylinders, (e) a high pressure chamber to which said power
hydraulic pressure source is connected, and (f) a high-pressure
supply valve which is disposed between said high pressure chamber
and said small diameter chamber and which is to be switched from a
closed state to an open state by forward movement of said stepped
piston.
[0111] Since the mechanical pressure-increasing device includes the
stepped piston, the hydraulic pressure of the manual hydraulic
pressure source can be increased based on, for example, a ratio
between a pressure receiving area of the large diameter portion and
a pressure receiving area of the small diameter portion. In this
sense, the mechanical pressure-increasing device may be referred to
as a boosting mechanism, and the hydraulic pressure supplied from
the mechanical pressure-increasing device may be referred to as a
servo pressure. Further, the high pressure generator may be
referred to as a pressure increasing mechanism.
[0112] (18) The brake system according to mode (17),
[0113] wherein said high-pressure-side check valve is disposed
between said high pressure chamber and said power hydraulic
pressure source,
[0114] and wherein said high-pressure-side check valve is
configured to allow flow of a working fluid in a direction toward
said high pressure chamber away from said power hydraulic pressure
source, and to inhibit flow of the working fluid in a direction
opposite to said direction toward said high pressure chamber away
from said power hydraulic pressure source.
[0115] Further, since the high-pressure-side check valve is
disposed between the high pressure chamber and the power hydraulic
pressure source, the flow of the working fluid between the power
hydraulic pressure source and the high pressure chamber is
inhibited when the hydraulic pressure of the power hydraulic
pressure source is not higher than the hydraulic pressure of the
high pressure chamber. It is therefore possible to satisfactorily
prevent the hydraulic pressure of the small diameter chamber from
becoming lower than the hydraulic pressure of the large diameter
chamber.
[0116] (19) The brake system according to mode (17) or (18),
[0117] wherein said high pressure generator includes a manual-side
check valve disposed between said manual hydraulic pressure source
and an output side portion of said mechanical pressure-increasing
device,
[0118] and wherein said manual-side check valve is configured to
allow flow of the working fluid in a direction toward said
mechanical pressure-increasing device away from said manual
hydraulic pressure source, and to inhibit flow of the working fluid
in a direction opposite to said direction toward said mechanical
pressure-increasing device away from said manual hydraulic pressure
source.
[0119] Owing to the manual-side check valve, the hydraulic pressure
outputted by the mechanical pressure-increasing device is prevented
from flowing back to the manual hydraulic pressure source.
[0120] Further, in a case in which the hydraulic pressure of the
small diameter chamber cannot be increased more due to inhibition
of forward movement of the stepped piston of the mechanical
pressure-increasing device (e.g., due to sticking of the piston,
due to inhibition of further forward movement of the piston upon
contact of the piston with a stopper that limits the forward
movement of the piston, due to inhibition of forward movement of
the piston by inhibition of flow of the working fluid between the
power hydraulic pressure source and the mechanical
pressure-increasing device by the high-pressure-side check valve),
when the hydraulic pressure of the manual hydraulic pressure source
becomes higher than the hydraulic pressure of the mechanical
pressure-increasing device, the hydraulic pressure of the manual
hydraulic pressure source is supplied to the common passage via the
manual-side check valve. In this instance, the hydraulic pressure
of the manual hydraulic pressure source is supplied to the common
passage, without the hydraulic pressure being increased.
[0121] The output side portion of the mechanical
pressure-increasing device includes the small diameter chamber,
because the hydraulic pressure of the small diameter chamber is
equal to the hydraulic pressure outputted by the mechanical
pressure-increasing device.
[0122] It is noted that the manual-side check valve may be disposed
inside the housing of the mechanical pressure-increasing device, or
may be disposed in a midway of a pressure-increasing-device-bypass
passage which is provided to bypass the housing of the mechanical
pressure-increasing device and which interconnect the output side
portion of the mechanical pressure-increasing device and the manual
hydraulic pressure source.
[0123] (20) The brake system according to any one of modes
(16)-(19), wherein said mechanical pressure-increasing device
includes a communication passage via which said small diameter
chamber and said large diameter chamber are to be in communication
with each other when said stepped piston is being positioned in a
reverse end position.
[0124] When the small diameter chamber and the large diameter
chamber are in communication with each other with the stepped
piston being positioned in the reverse end position, the hydraulic
pressure of the common passage, i.e., the hydraulic pressure of
each brake cylinder can be returned to the manual hydraulic
pressure source via the mechanical pressure-increasing device upon
release of a brake operation.
[0125] (21) A brake system, characterized by comprising:
[0126] a plurality of hydraulic brakes provided for respective
wheels of a vehicle, and configured to be activated by hydraulic
pressures of respective brake cylinders thereof so as to restrain
rotations of the respective wheels;
[0127] a manual hydraulic pressure source which is configured to
generate hydraulic pressure by operation of a brake operating
member by an operator;
[0128] a power hydraulic pressure source which is configured to
generate hydraulic pressure by supply of electric energy
thereto;
[0129] a high pressure generator which is configured to generate
hydraulic pressure that is higher than the hydraulic pressure of
said manual hydraulic pressure source, by utilizing the hydraulic
pressure of said power hydraulic pressure source;
[0130] a common passage to which a first brake cylinder, a second
brake cylinder and said high pressure generator are connected, said
first brake cylinder being one of said brake cylinders of said
hydraulic brakes and being connected to said common passage via a
first individual passage, said second brake cylinder being one of
said brake cylinders that is other than said first brake cylinder
and being connected to said common passage via a second individual
passage that is other than said first individual passage;
[0131] a first manual-pressure-source passage connecting said first
individual passage and said manual hydraulic pressure source;
[0132] a first manual-pressure-source cut-off valve provided in
said first manual-pressure-source passage;
[0133] a first valve provided in a portion of a pressure supply
passage which is located between a connected portion of said
pressure supply passage and a connected portion of said common
passage, said pressure supply passage including said first
individual passage, second individual passage and common passage,
said pressure supply passage being connected at said connected
portion thereof to said first manual-pressure-source passage, said
common passage being connected at said connected portion thereof to
said high pressure generator; and
[0134] a pressure-supply control device configured to control
supply of the hydraulic pressure to each of said brake cylinders,
by controlling at least said first valve and first
manual-pressure-source cut-off valve.
[0135] By placing the first valve in the open state and placing the
first manual-pressure-source cut-off valve in the closed state, the
first brake cylinder can be isolated from the master cylinder and
brought into communication with the high pressure generator. It is
therefore possible to supply the hydraulic pressure of the high
pressure generator to the first and second brake cylinders.
[0136] Further, by placing the first valve in the closed state and
placing the first manual-pressure-source cut-off valve in the open
state, the first brake cylinder can be isolated from the high
pressure generator and the second brake cylinder and brought into
communication with the manual hydraulic pressure source, so that
the hydraulic pressure of the high pressure generator is supplied
to the second brake cylinder.
[0137] The technical features described in any one of the above
modes (1)-(20) can be employed in the brake system described in
this mode.
[0138] (22) A brake system, characterized by comprising:
[0139] a plurality of hydraulic brakes provided for respective
wheels of a vehicle, and configured to be activated by hydraulic
pressures of respective brake cylinders thereof so as to restrain
rotations of the respective wheels;
[0140] a manual hydraulic pressure source which is configured to
generate hydraulic pressure by operation of a brake operating
member by an operator;
[0141] a power hydraulic pressure source which is configured to
generate hydraulic pressure by supply of electric energy
thereto;
[0142] a pressure increasing mechanism which is disposed among said
power hydraulic pressure source, said manual hydraulic pressure
source and said hydraulic brakes, and which is to be activated
mechanically by the hydraulic pressure of said manual hydraulic
pressure source so as to output the hydraulic pressure that is to
be supplied to said brake cylinders of said hydraulic brakes,
[0143] said brake system being characterized in that:
[0144] said pressure increasing mechanism includes (a) a mechanical
pressure-increasing device configured to increase the hydraulic
pressure of said manual hydraulic pressure source and to output the
increased hydraulic pressure and (b) a high-pressure-side check
valve disposed between said mechanical pressure-increasing device
and said power hydraulic pressure source; and
[0145] said high-pressure-side check valve is configured to allow
flow of a working fluid in a direction toward said mechanical
pressure-increasing device away from said power hydraulic pressure
source, and to inhibit flow of the working fluid in a direction
opposite to said direction toward said mechanical
pressure-increasing device away from said power hydraulic pressure
source.
[0146] The pressure increasing mechanism described in this mode is
an example of the high pressure generator. The technical features
described in any one of the above modes (1)-(21) can be employed in
the brake system described in this mode.
[0147] (23) The brake system according to any one of modes
(1)-(22), comprising:
[0148] a fluid-leakage possibility detecting device configured to
detect presence of possibility of fluid leakage in said brake
system; and
[0149] an electromagnetic-valve controlling portion configured to
place at least said first valve in the closed state when the
presence of possibility of fluid leakage is detected by said
fluid-leakage possibility detecting device.
[0150] (24) The brake system according to mode (23), wherein said
fluid-leakage possibility detecting device is configured to detect
the presence of possibility of fluid leakage, upon satisfaction of
at least one of conditions that consist of (a) a condition that the
hydraulic pressure in said common passage is lower than a
common-passage-pressure-based judgment threshold value, (b) a
condition that the hydraulic pressure in a brake line including
said first brake cylinder and/or the hydraulic pressure in a brake
line including said second brake cylinder is lower than a
brake-line-pressure-based judgment threshold value, (c) a condition
that an amount of a working fluid reserved in a reservoir reserving
the working fluid used in said brake cylinders of said hydraulic
brakes, is smaller than a reserved-fluid-amount-based judgment
threshold value, and (d) a condition that the hydraulic pressure of
said power hydraulic pressure source is lower than a
fluid-source-pressure-based judgment threshold value.
[0151] Since the fluid-leakage possibility detecting device is
configured to detect the presence of possibility of fluid leakage,
there is a case in which the fluid leakage does not actually occur
even when the presence of possibility of fluid leakage is detected
by the fluid-leakage possibility detecting device. Further, there
is a case in which an amount of fluid leakage is actually very
little when the presence of possibility of fluid leakage is
detected. Moreover, it is common that it is not possible to specify
which part of the brake system suffers from the fluid leakage. In
either of these cases, by placing a communication shut-off valve in
a closed state upon detection of the presence of possibility of
fluid leakage, it is possible to avoid the fluid leakage occurring
in one of the brake cylinders (or one of the brake lines) from
influencing the other of the brake cylinders (or the other of the
brake lines), and accordingly to improve reliability of the brake
system.
[0152] It is possible to regard that the possibility of fluid
leakage is present in a case in which the hydraulic pressure in the
common passage is not increased at all or not sufficiently
increased (namely, remains lower than the
common-passage-pressure-based judgment threshold value in spite of
elapse of a given length of time after initiation of activation of
the hydraulic pressure source) when the hydraulic pressure source
has been activated at least for a given length of time with the
hydraulic pressure source being in communication with the common
passage.
[0153] Further, it is possible to regard that the possibility of
fluid leakage is present also in a case in which the hydraulic
pressure in the brake line including the first brake cylinder
or/and the hydraulic pressure in the brake line including the
second brake cylinder is lower than the brake-line-pressure-based
judgment threshold value upon request of activations of the
hydraulic brakes (i.e., upon operation of a brake operating member,
or upon request of activation of an automatic brake). The
brake-line-pressure-based judgment threshold value may be a value
determined depending upon a required braking-force magnitude (i.e.,
a value dependent on a state of operation of the brake operating
member or a value dependent on a required automatic-braking-force
magnitude), or may be a considerably small value that is close to
zero.
[0154] The detection of the presence of possibility of fluid
leakage on the basis of an amount of the working fluid reserved in
the reservoir can be made irrespective of states of activations of
the hydraulic brakes or a state of operation of the brake operating
member. It is possible to regard that the possibility of presence
of fluid leakage is present, for example, in a case in which the
hydraulic pressure is not sufficiently increased even when the
hydraulic pressure source has been activated for a given length of
time.
BRIEF DESCRIPTION OF DRAWINGS
[0155] FIG. 1 is a view schematically showing an entirety of a
vehicle in which a hydraulic brake system that is common to
embodiments of the present invention is installed.
[0156] FIG. 2 is a diagram of a hydraulic circuit of the hydraulic
brake system according to Embodiment 1 of the present
invention.
[0157] FIG. 3 is a cross sectional view showing a
pressure-increasing linear control valve and a pressure-reducing
linear control valve that are included in the hydraulic brake
system.
[0158] FIG. 4 is a flow chart representing an initial-check program
stored in a memory portion of a brake ECU that is included in the
hydraulic brake system.
[0159] FIG. 5 is a flow chart representing a
hydraulic-pressure-supply control program stored in the memory
portion of the brake ECU that is included in the hydraulic brake
system.
[0160] FIG. 6 is a view showing a state upon execution of the
hydraulic-pressure-supply control program in the hydraulic brake
system (in case of normality of the system).
[0161] FIG. 7 is a view showing another state upon execution of the
hydraulic-pressure-supply control program in the hydraulic brake
system (in case of failure of a control system of the brake
system).
[0162] FIG. 8 is a view showing still another state upon execution
of the hydraulic-pressure-supply control program in the hydraulic
brake system (in case of presence of possibility of fluid
leakage).
[0163] FIG. 9 is a diagram of a hydraulic circuit of the hydraulic
brake system according to Embodiment 2 of the present
invention.
[0164] FIG. 10 is a view showing a state upon execution of the
hydraulic-pressure-supply control program in the hydraulic brake
system (in case of normality of the system).
[0165] FIG. 11 is a view showing another state upon execution of
the hydraulic-pressure-supply control program in the hydraulic
brake system (in case of failure of a control system of the brake
system).
[0166] FIG. 12 is a view showing still another state upon execution
of the hydraulic-pressure-supply control program in the hydraulic
brake system (in case of presence of possibility of fluid
leakage).
[0167] FIG. 13 is a flow chart representing a front/rear cut-off
valve & right/left cut-off valve control program stored in the
memory portion of the brake ECU that is included in the hydraulic
brake system.
[0168] FIG. 14 is a flow chart representing a front/rear cut-off
valve & right/left cut-off valve control program stored in the
memory portion of the brake ECU that is included in a hydraulic
brake system according to Embodiment 3 of the present
invention.
[0169] FIG. 15 is a flow chart representing another front/rear
cut-off valve & right/left cut-off valve control program stored
in the memory portion of the brake ECU.
[0170] FIG. 16 is a flow chart representing still another
front/rear cut-off valve & right/left cut-off valve control
program stored in the memory portion of the brake ECU.
[0171] FIG. 17 is a flow chart representing still another
front/rear cut-off valve & right/left cut-off valve control
program stored in the memory portion of the brake ECU.
[0172] FIG. 18 is a diagram of a hydraulic circuit of a hydraulic
brake system according to Embodiment 4 of the present
invention.
MODES FOR CARRYING OUT THE INVENTION
[0173] Hereinafter, a brake system as an embodiment of the present
invention will be described with reference to drawings.
[0174] There will be first described a vehicle on which a hydraulic
brake system as the brake system according to the embodiment 1 is
installed.
[0175] This vehicle is a hybrid vehicle including driving units in
the form of an electric motor and an engine, so that front left and
right wheels 2, 4 as drive wheels are to be driven by a drive
system 10 including an electric drive device 6 and an
internal-combustion drive device 8. A drive power of the drive
system 10 can be transmitted to the front left and right wheels 2,
4 via drive shafts 12, 14. The internal-combustion drive device 8
includes an engine 16 and an engine ECU 18 that is configured to
control activation of the engine 16. The electric drive device 6
includes a driving electric motor 20, a storage device 22, a motor
generator 24, a conversion device 26, a motor ECU 28 and a power
dividing mechanism 30. The electric motor 20, motor generator 24,
engine 16 and power dividing mechanism 30 (to which the electric
motor 20, motor generator 24 and engine 16 are connected) are
controlled so as to selectively establish a state in which only a
driving torque of the electric motor 20 is transmitted to an output
member 32, a state in which a driving torque of the engine 16 and
the driving torque of the electric motor 20 are both transmitted to
the output member 32, and a state in which an output of the engine
16 is outputted to the motor generator 24 and the output member 32.
The driving force transmitted to the output member 32 is
transmitted to the drive shafts 12, 14 via a speed reducer and
differential gears.
[0176] The conversion device 26 includes an inverter, and is
controlled by the motor ECU 28. With electric current control of
the inverter, the conversion device 26 selectively establishes at
least a driving state in which the electric motor 20 is rotated by
electric energy supplied from the storage device 22 to the electric
motor 20 and a charging state in which the conversion device 26
serves as a generator upon regenerative braking so as to charge the
storage device 22 with electric energy. During the charging state,
a regenerative braking torque is applied to each of the front left
and right wheels 2, 4. In this sense, the electric drive device 6
can be considered as a regenerative braking device.
[0177] The hydraulic brake system includes brake cylinders 42 of
respective hydraulic brakes 40 provided for the respective front
left and right wheels 2, 4, brake cylinders 52 of respective
hydraulic brakes 50 provided for the respective rear left and right
wheels 46, 48 (see FIGS. 2, 9 and 18), and a hydraulic-pressure
controlling portion 54 configured to control hydraulic pressures of
the respective brake cylinders 42, 52. The hydraulic-pressure
controlling portion 54 is to be controlled by a brake ECU 56 that
is constituted principally by a computer.
[0178] Further, the vehicle is provided with a hybrid ECU 58. The
hybrid ECU 58, brake ECU 56, engine ECU 18 and motor ECU 28 are
connected to one another via CAN (car area network) 59, so that
these ECUs 58, 56, 18, 28 are communicable to one another, and
required information are transmitted among the ECUs 58, 56, 18, 28
as needed.
[0179] The present hydraulic brake system is installable on not
only a hybrid vehicle but also a plug-in hybrid vehicle, an
electric vehicle and a fuel battery vehicle. In an electric
vehicle, the internal-combustion drive device 8 is not required. In
a fuel battery vehicle, the driving motor is driven by, for
example, a fuel battery stack.
[0180] Further, the present hydraulic brake system is installable
also on an internal-combustion drive vehicle. In such a vehicle not
equipped with the electric drive device 6, a regenerative braking
torque is not applied to the driving wheels 2, 4 so that a
regenerative cooperative control is not executed.
[0181] The hydraulic brake system will be next described. In the
following description, each of the brake cylinders, hydraulic
brakes and electromagnetic valves will be referred together with,
as a suffix, one of reference signs (FR, FL, RR, RL) indicative of
the respective front right, front left, rear right and rear left
wheels, where it should be clarified which one of the four wheels
the referred brake cylinder, hydraulic brake or electromagnetic
valve corresponds to. However, each of the brake cylinders,
hydraulic brakes and electromagnetic valves will be referred
without such reference signs, where it is referred to as a
representative of those provided for the four wheels, or where the
above-described clarification is not required.
Embodiment 1
[0182] The present brake system includes a brake circuit shown FIG.
2 in which reference sign "60" denotes a brake pedal as a brake
operating member, reference sign "62" denotes a master cylinder as
manual hydraulic pressure sources which is configured to generate
hydraulic pressure by operation of the brake pedal 60, and
reference sign "64" denotes a power hydraulic pressure source
including a pump device 65 and an accumulator 66. The hydraulic
brakes 40, 50 are to be activated by hydraulic pressures of the
respective brake cylinders 42, 52. In the present embodiment, each
of the hydraulic brakes 40, 50 is a disk brake.
[0183] It is noted that each of the hydraulic brakes 40, 50 may be
a drum brake. It is further noted that each of the hydraulic brakes
40 provided for the front wheels 2, 4 may be a disk brake while
each of the hydraulic brakes 50 provided for the rear wheels 46, 48
may be a drum brake.
[0184] The master cylinder 62 is a tandem cylinder including two
pressurizing pistons 68, 69, and has pressurizing chambers 70, 72
such that the pressurizing chamber 70 is located on a front side of
the pressurizing piston 68 while the pressurizing chamber 72 is
located on a front side of the second pressurizing piston 69. In
the present embodiment, each of the pressurizing chambers 70, 72
serve as a manual hydraulic pressure source. Further, to the
pressurizing chambers 72, 70, the brake cylinders 42FL, 42FR of the
hydraulic brakes 40FL, 40FR provided for the respective front left
and right wheels 2, 4 are connected via respective master cylinder
passages 74, 76 as manual-pressure-source passages.
[0185] Further, the pressurizing chambers 70, 72 are brought into
communication with a reservoir 78, when the pressurizing pistons
68, 69 reach respective reverse end positions. The reservoir 78
defines therein an inside space that is partitioned into a
plurality of reservoir chambers 80, 82, 84 configured to store
therein working fluid. The reservoir chambers 80, 82 are provided
for the pressurizing chambers 70, 72, while the reservoir chamber
84 is provided for the pump device 65.
[0186] In the power hydraulic pressure source 64, the pump device
65 includes a pump 90 and a pump motor 92, so that the working
fluid is pumped from the reservoir chamber 84 of the reservoir 78
by activation of the pump 90, and the pumped working fluid is
stored in the accumulator 66. The pump motor 92 is controlled such
that the pressure of the working fluid stored in the accumulator 66
is held within a predetermined range. Further, a relief valve 94 is
provided to prevent an excessive increase of pressure discharged
from the pump 90.
[0187] A pressure increasing mechanism 100 as a high pressure
generator is disposed between the power hydraulic pressure source
64 and the master cylinder passage 76. The pressure increasing
mechanism 100 includes a housing 102 and a stepped piston 104 which
is fluid-tightly, slidably fitted in the housing 102. The pressure
increasing mechanism 100 has a large diameter chamber 110 located
on a side of the a large diameter portion of the stepped piston 104
and a small diameter chamber 112 located on a side of a small
diameter portion of the stepped piston 104.
[0188] The small diameter chamber 112 can be in communication with
a high pressure chamber 114 that is connected to the power
hydraulic pressure source 64. Further, a high-pressure supply valve
116 is disposed between the small diameter chamber 112 and the high
pressure chamber 114. The high-pressure supply valve 116, which is
a normally-close valve, includes a valve body 120, a valve seat 122
and a spring 124. The spring 124 generates a biasing force that
causes the valve body 120 to be forced against the valve seat
122.
[0189] In the small diameter chamber 112, a valve opening member
125 is provided to be opposed to the valve body 120. A spring 126
is disposed between the valve opening member 125 and the stepped
piston 104, and generates a biasing force that causes the valve
opening member 125 to be moved in a direction away from the stepped
piston 104.
[0190] Between the housing 102 and a stepped portion of the stepped
piston 104, a spring 128 (i.e., return spring) is disposed to bias
the stepped piston 104 in the rearward direction. It is noted that
a stopper (not shown) is disposed between the stepped piston 104
and the housing 102, so as to define a forward end position of the
stepped piston 104.
[0191] Further, the stepped piston 104 has a communication passage
130 through which the large diameter chamber 110 and the small
diameter chamber 112 are to be in communication with each other. At
least when the stepped piston 104 is positioned in the reverse end
position, the stepped piston 104 is distant from the valve opening
member 125 so that the large diameter chamber 110 and the small
diameter chamber 112 are in communication with each other via the
communication passage 130. When the stepped piston 104 is moved
forwardly so as to be brought into contact with the valve opening
member 125, the communication between the large diameter chamber
110 and the small diameter chamber 112 is cut off.
[0192] In the present embodiment, a mechanical pressure-increasing
device 134 is constituted by, for example, the above-described
housing 102, stepped piston 104, high-pressure supply valve 116 and
valve opening member 125.
[0193] The high pressure chamber 114 and the power hydraulic
pressure source 64 are connected through a high-pressure supplying
passage 131 that is provided with a high-pressure-side check valve
132 which allows flow of the working fluid in a direction away from
the power hydraulic pressure source 64 toward the high pressure
chamber 114 and which inhibits flow of the working fluid in the
opposite direction away from the high pressure chamber 114 toward
the power hydraulic pressure source 64. When the hydraulic pressure
of the power hydraulic pressure source 64 is higher than the
hydraulic pressure in the high pressure chamber 114, the
high-pressure-side check valve 132 allows flow of the working fluid
in the direction away from the power hydraulic pressure source 64
toward the high pressure chamber 114. However, when the hydraulic
pressure of the power hydraulic pressure source 64 is not higher
than the hydraulic pressure in the high pressure chamber 114, the
high-pressure-side check valve 132 is placed in its closed state
thereby inhibiting not only the fluid flow in the opposite
direction away from the high pressure chamber 114 toward the power
hydraulic pressure source 64 but also the fluid flow in the
direction away from the power hydraulic pressure source 64 toward
the high pressure chamber 114. Therefore, even if a fluid leakage
takes place in the power hydraulic pressure source 64, the flow of
the working fluid in the opposite direction away from the high
pressure chamber 114 toward the power hydraulic pressure source 64
is prevented whereby a reduction of the hydraulic pressure in the
small diameter chamber 112 is prevented.
[0194] Further, between the master cylinder passage 70b and an
output side of the mechanical pressure-increasing device 134 (or
between the master cylinder passage 70b and the small diameter
chamber 112), a bypass passage 136 is disposed to interconnect
therebetween, bypassing the mechanical pressure-increasing device
134. The bypass passage 136 is provided with a manual-side check
valve 138 which allows flow of the working fluid in a direction
away from the master cylinder passage 74 toward the output side of
the mechanical pressure-increasing device 134 and which inhibits
flow of the working fluid in the opposite direction away from the
output side of the mechanical pressure-increasing device 134 toward
the master cylinder passage 74.
[0195] In the pressure increasing mechanism 100, when the hydraulic
pressure is supplied to the large diameter chamber 110 from the
pressurizing chamber 72 of the master cylinder 14, the working
fluid is supplied to the small diameter chamber 112 via the
communication passage 130.
[0196] When a force (generated by the hydraulic pressure in the
large diameter chamber 110) acting on the stepped piston 104 in the
forward direction becomes larger than the biasing force of the
return spring 128, the stepped piston 104 is moved in the forward
direction. When the communication passage 130 is closed by the
valve opening member 125 as a result of contact of the stepped
piston 104 with the valve opening member 125, the hydraulic
pressure in the small diameter chamber 112 is increased and
outputted.
[0197] Further, when the high-pressure supply valve 116 is turned
to the open state as a result of forward movement of the valve
opening member 125, the highly-pressurized working fluid is
supplied from the high pressure chamber 114 to the small diameter
chamber 112 whereby the hydraulic pressure in the small diameter
chamber 112 is increased. On the other hand, the pressure of the
working fluid stored in the accumulator 66 is higher than the
pressure in the high pressure chamber 114, the hydraulic pressure
in the accumulator 66 is supplied to the high pressure chamber 114
via the high-pressure-side check valve 132 and then supplied to the
small diameter chamber 112.
[0198] The hydraulic pressure in the large diameter chamber 110 is
adjusted such that the force (=hydraulic pressure in the master
cylinder 62.times.pressure-receiving area) acting on a large
diameter side of the stepped piston 104 and the force (=output
hydraulic pressure.times.pressure-receiving area) acting on a small
diameter side of the stepped piston 104 are balanced to each other,
and then the adjusted hydraulic pressure in the large diameter
chamber 110 is outputted. In this sense, the pressure increasing
mechanism 100 may be referred to as a boosting mechanism.
[0199] Further, owing to the manual-side check valve 138, the
hydraulic pressure outputted from the mechanical
pressure-increasing device 134 is prevented from flowing toward the
master cylinder passage 74.
[0200] On the other hand, when the hydraulic pressure in the
accumulator 66 is not higher than the hydraulic pressure in the
high pressure chamber 114, the working fluid is inhibited, by the
high-pressure-side check valve 132, from flowing in either
direction between the accumulator 66 and the high pressure chamber
114 whereby the stepped piston 104 cannot be moved further in the
forward direction. Further, in this instance, there is a case where
the stepped piston 104 cannot be moved further in the forward
direction as a result of contact of the stepped piston 104 with the
above-described stopper. When the hydraulic pressure in the
pressurizing chamber 72 becomes, from this state, higher than the
hydraulic pressure in the small diameter chamber 112, the hydraulic
pressure is supplied to the output side of the mechanical
pressure-increasing device 134 via the
pressure-increasing-device-bypass passage 136 and the manual-side
check valve 138.
[0201] On the other hands, the brake cylinders 42FL, 42FR provided
for the front left and right wheels 2, 4 and the brake cylinders
52RL, 52RR provided for the rear left and right wheels 46, 48 are
connected to a common passage 152 via respective individual
passages 150FL, 150FR, 150RL, 150RR, respectively.
[0202] The individual passages 150FL, 150FR, 150RL, 150RR are
provided with respective pressure holding valves (SHij: i=F, R;
j=L, 153FR, 153FL, 153RR, 153RL. Between the brake cylinders 42FL,
42FR, 52RL, 52RR and the reservoir 78, there are disposed pressure
reducing valves (SRij: i=F, R; j=L, R) 156FL, 156FR, 156RL,
156RR.
[0203] In the present embodiment, each of the pressure holding
valves 153FL, 153RR provided for the front left wheel 2 and rear
right wheel 48 is a normally-open electromagnetic valve that is to
be placed in an open state when electric current is not being
supplied to a solenoid thereof. Meanwhile, each of the pressure
holding valves 153FR, 153RL provided for the front right wheel 4
and rear left wheel 46 is a normally-closed electromagnetic valve
that is to be placed in a closed state when electric current is not
being supplied to a solenoid thereof.
[0204] Thus, one and the other of the pressure holding valves
153FL, 153FR provided for the front left and right wheels 2, 4 are
constituted by the normally-open electromagnetic valve and the
normally-closed electro-magnetic valve, respectively. One and the
other of the pressure holding valves 153RL, 153RR provided for the
rear left and right wheels 46, 48 are constituted by the
normally-open electromagnetic valve and the normally-closed
electromagnetic valve, respectively.
[0205] Further, each of the pressure holding valves 153FL, 153RR
provided for two wheels (i.e., the front left wheel 2 and rear
right wheel 48) which are located in respective positions diagonal
to each other, is constituted by the normally-open electromagnetic
valve. Each of the pressure holding valves 153FR, 153RL provided
for other two wheels (i.e., the front right wheel 4 and rear left
wheel 46) which are located in respective positions diagonal to
each other, is constituted by the normally-closed electromagnetic
valve.
[0206] Further, each of the pressure reducing valves 156FL, 156FR,
156RR is constituted by a normally-closed electromagnetic valve,
while the pressure reducing valve 156RL provided for the rear left
wheel 46 is constituted by a normally-open electromagnetic
valve.
[0207] To the common passage 152 to which the brake cylinders 42,
52 are connected, the power hydraulic pressure source 64 and the
pressure increasing mechanism 100 are also connected.
[0208] The power hydraulic pressure source 64 is connected to the
common passage 152 via a controlled-pressure passage 170. The
controlled-pressure passage 170 is provided with a
pressure-increasing linear control valve (SLA) 172. A
pressure-reducing linear control valve (SLR) 176 is provided
between the controlled-pressure passage 170 and the reservoir 78.
With the pressure-increasing linear control valve 172 and
pressure-reducing linear control valve 176 being controlled, the
hydraulic pressure outputted by the power hydraulic pressure source
64 is controlled, and the controlled hydraulic pressure is supplied
to the common passage 152. The pressure-increasing linear control
valve 172 and the pressure-reducing linear control valve 176
cooperate to constitute an output hydraulic-pressure control valve
device 178. Further, each of the pressure-increasing linear control
valve 172 and pressure-reducing linear control valve 176 may be
referred to as an output hydraulic-pressure control valve. Each of
the pressure-increasing linear control valve 172 and
pressure-reducing linear control valve 176 is a normally-closed
electromagnetic valve which is to be placed in a closed state when
electric current is not being supplied to a solenoid thereof, and
which is configured to output hydraulic pressure whose amount is
continuously controlled by continuously controlling an amount of
the electric current supplied to the solenoid.
[0209] As shown in FIG. 3, each of the pressure-increasing linear
control valve 172 and pressure-reducing linear control valve 176
includes a valve body 180, a valve seat 182 (that cooperates with
the valve body 120 to constitute a seating valve), a spring 184 and
a solenoid 186. The spring 184 generates a biasing force F2 forcing
the valve body 180 in a direction toward the valve seat 182. The
solenoid 186, when electric current is being applied thereto,
generates a driving force F1 forcing the valve body 180 in a
direction away from the valve seat 182. Further, in the
pressure-increasing linear control valve 172, a
pressure-difference-based force F3, which is generated based on a
difference between pressure in the power hydraulic pressure source
64 and pressure in the common passage 152, acts on the valve body
180, forcing the valve body 180 to be displaced in a direction away
from the valve seat 182. In the pressure-reducing linear control
valve 176, a pressure-difference-based force F3, which is generated
based on a difference between pressure in the common passage 152
(controlled-pressure passage 170) and pressure in the reservoir 78,
acts on the valve body 180, forcing the valve body 180 to be
displaced in a direction away from the valve seat 182 (F1+F3: F2).
In each of the valves 172, 176, the pressure-difference-based force
F3 is controlled by controlling the electric current that is
supplied to the solenoid 186, whereby the hydraulic pressure in the
controlled-pressure passage 170 is controlled. Further, it can be
also considered that the hydraulic pressure in the common passage
152 is controlled by controlling the pressure-increasing linear
control valve 172 and pressure-reducing linear control valve
176.
[0210] The pressure increasing mechanism 100 is connected to the
common passage 152 via a servo pressure passage 190 that is
provided with a pressure increasing mechanism cut-off valve (SREG)
192 as a high-pressure-generator cut-off valve. The pressure
increasing mechanism cut-off valve 192 is constituted by a
normally-open electromagnetic valve.
[0211] On the other hand, the master cylinder passage 74 is
connected to a portion of the individual passage 150FL provided for
the front left wheel 2, which portion is located on a downstream
side of the pressure holding valve 153FL. Meanwhile, the master
cylinder passage 76 is connected to a portion of the individual
passage 150FR provided for the front right wheel 4, which portion
is located on a downstream side of the pressure holding valve
153FR. A master-cylinder cut-off valve (SMCFR) 194FL as a
manual-pressure-source cut-off valve is provided on a midway of the
master cylinder passage 74, while another master-cylinder cut-off
valve (SMCFL) 194FR as another manual-pressure-source cut-off valve
is provided on a midway of the master cylinder passage 76. The
master-cylinder cut-off valve 194FL is a normally-closed
electromagnetic valve while the master-cylinder cut-off valve 194FR
is a normally-open electromagnetic valve.
[0212] Further, a stroke simulator 200 is connected to the master
cylinder passage 74 via a simulator controlling valve 202 that is a
normally-closed electromagnetic valve.
[0213] In the present embodiment, as described above, the
above-described power hydraulic pressure source 64, output
hydraulic-pressure control valve device 178, master-cylinder
cut-off valves 194, pressure holding valve 153, pressure reducing
valves 156 and pressure increasing mechanism cut-off valve 192
cooperate to constitute the hydraulic-pressure controlling portion
54 that is controlled based on commands supplied from the brake ECU
56. As shown in FIG. 1, the brake ECU56 is constituted principally
by a computer including an executing portion, an input/output
portion and a memory portion. To the input/output portion, there
are connected, for example, a brake switch 218, a stroke sensor
220, a master-cylinder pressure sensor 222, an accumulator pressure
sensor 224, a brake-cylinder pressure sensor 226, a level warning
switch 228, a wheel velocity sensor 230, a door opening/closing
switch 232, an ignition switch 234, an acceleration switch 236 and
the above-described hydraulic-pressure controlling portion 54.
[0214] The brake switch 218 is a switch, which is turned from its
OFF state to its ON state when the brake pedal 60 is operated.
[0215] The stroke sensor 220 is configured to detect an operating
stroke (STK) of the brake pedal 60. In the present embodiment, the
stroke sensor 220 is constituted by two sensors both of which are
configured to detect the operating stroke of the brake pedal 60 in
the same manner.
[0216] The master-cylinder pressure sensor 222 is constituted by
two sensors that are provided in the respective master cylinder
passages 74, 76. The two sensors of the master-cylinder pressure
sensor 222 are configured to detect the hydraulic pressures (PMCFL,
PMCFR) in the pressurizing chambers of the master cylinder 62,
which are equal in magnitude to each other in most cases.
[0217] Thus, in the present embodiment, each of the stroke sensor
220 and the master-cylinder pressure sensor 222 constitutes two
lines, so that, even in the event of failure of one of the two
sensors of each of the stroke sensor 220 and the master-cylinder
pressure sensor 222, a brake operating state can be detected by the
other of the two sensors which functions normally.
[0218] The accumulator pressure sensor 224 is configured to detect
pressure (PACC) of working fluid stored in the accumulator 66.
[0219] The brake-cylinder pressure sensor 226 is provided in the
common passage 152, and is configured to detect pressure (PWC) in
each of the brake cylinders 42, 52. When each of the pressure
holding valves 153 is placed in the open state, the common passage
152 is held in communication with each of the brake cylinders 42,
52, so that the hydraulic pressure in each of the brake cylinders
42, 52 can be made equal to the hydraulic pressure in the common
passage 152.
[0220] The level warning switch 228 is a switch which is to be
turned to the OFF state when the working fluid reserved in the
reservoir 78 becomes not larger than a predetermined amount. In the
present embodiment, when the amount of the working fluid reserved
in one of the three reservoir chambers 80, 82, 84 becomes not
larger than a predetermined amount, the level warning switch 228 is
turned to the OFF state.
[0221] The wheel velocity sensor 230 is provided for each of the
front right wheel 4, front left wheel 2, rear right wheel 48 and
rear left wheel 46, so as to detect rotational velocity of each of
the wheels. A running velocity of the vehicle is obtained based on
the rotational velocities of the four wheels.
[0222] The door opening/closing switch 232 is configured to detect
opening and closing of a door of the vehicle. The switch 232 may be
configured to either detect the opening/closing of a door of a
vehicle-operator side or detect the opening/closing of any one of
the other doors. The door opening/closing switch 232 may be
constituted by a door courtesy lamp switch of the vehicle.
[0223] The ignition switch (IGSW) 234 is a main switch of the
vehicle. The acceleration switch 236 is a switch that is to be
placed in ON state when an acceleration operating member (not
shown) is being operated.
[0224] Further, to the CAN 59, there are connected, for example, a
following distance ECU 240 and a collision avoidance ECU 242. The
brake ECU 56 controls the hydraulic-pressure controlling portion
54, for example, in accordance with braking commands supplied from
these ECUs 240, 242.
[0225] Moreover, the memory portion stores therein, for example,
various programs and tables.
[0226] <Initial Checks>
[0227] In the present embodiment, checks are carried out upon
satisfaction of a predetermined check starting condition. This
check starting condition is satisfied, for example, when the door
opening/closing switch 232 is turned to the ON state, and when a
brake operation is carried out for the first time after the
ignition switch 234 has been turned to the ON state.
[0228] FIG. 4 is a flow chart showing an initial checking program
that is executed at a predetermined time interval.
[0229] The execution of this initial checking program is initiated
with step S1 that is implemented to judge whether the predetermined
check starting condition is satisfied or not. When the check
starting condition is satisfied, step S2 is implemented to check
the control system, and step S3 is implemented to check possibility
of fluid leakage.
[0230] For detecting failure of the control system, for example, it
is judged whether or not there is a breaking of wire for each of
all the electromagnetic valves (e.g., pressure-increasing linear
control valve 172, pressure-reducing linear control valve 176,
pressure holding valve 153, pressure reducing valve 156,
master-cylinder cut-off valve 194, pressure increasing mechanism
cut-off valve 192), and it is judged whether or not there is a
breaking of wire for each of all the sensors (e.g., brake switch
218, stroke sensor 220, master-cylinder pressure sensor 222,
accumulator pressure sensor 224, brake-cylinder pressure sensor
226, wheel velocity sensor 230).
[0231] The possibility of the fluid leakage is checked, for
example, when the ignition switch 234 is turned to the ON state,
and when the brake operation is carried out. It is judged that
there is no fluid leakage, for example, (a) when the level warning
switch 228 is in the ON state, and (b) when there is established a
predetermined relationship between the stroke of the brake pedal 60
and the hydraulic pressure in the master cylinder 62 upon execution
of the brake operation. On the other hand, it is judged that there
is a possibility of fluid leakage, when the hydraulic pressure in
the master cylinder 62 is low relative to the stroke of the brake
pedal 60. Further, it is judged that there is a possibility of
fluid leakage, (c) when a value detected by the accumulator
pressure sensor 224 does not reach a fluid-leakage-judgment
threshold value even after continuation of activation of the pump
90 for a predetermined length of time, (d) when the value detected
by the brake-cylinder pressure sensor 226 is low relative to a
value detected by the master-cylinder pressure sensor 222 while the
regenerative cooperative control is not being carried out, and (e)
when it was judged that there was a possibility of fluid leakage
upon previous brake activation (when the hydraulic pressure in the
master cylinder 62 was supplied to the brake cylinders 42 for the
front left and right wheels 2, 4, while the pump pressure was
supplied to the brake cylinders 52 for the rear left and right
wheels 46, 48).
[0232] Thus, in the present embodiment, the possibility of the
fluid leakage is detected based on the above-described conditions
(a)-(e). There is a case where a fluid leakage does not actually
take place even when it is judged that there is a possibility of
the fluid leakage, because the above-described conditions (b)-(e)
could be satisfied by a factor other than the fluid leakage.
Further, there is a case where an amount of the fluid leakage is
small when the fluid leakage actually takes place. However, even in
these cases, it is judged that there is a possibility of the fluid
leakage, because it is not possible to assert that there is no
possibility of the fluid leakage.
[0233] <Brake Hydraulic Pressure Control>
[0234] Then, the hydraulic pressures supplied to the brake
cylinders 42, 52 are controlled based on result of the
above-described initial checks. FIG. 5 is a flow chart representing
a brake-hydraulic-pressure controlling program that is executed at
a predetermined time interval.
[0235] In step S11, it is judged whether a braking command is
issued or not. A positive judgment (YES) is obtained in step S11,
for example, when the brake switch 218 is in the ON state, and when
a command requesting activation of an automatic brake is issued.
Since there is a case where the automatic brake is activated upon
executions of a traction control, a vehicle stability control, a
following distance control and a collision avoidance control, it is
judged that the braking command is issued upon satisfaction of
conditions required for starting theses controls.
[0236] When it is judged that the braking command is issued, the
control flow goes to steps S12 and S13 that are implemented to read
results of the judgment as to whether or not there is a possibility
of the fluid leakage and the judgment as to whether or not the
control system suffers from the failure.
[0237] When negative judgments (NO) are obtained in both of these
judgments, namely, when the brake system functions normally (i.e.,
when it is judged that the control system functions normally and
that there is no possibility of the fluid leakage), the control
flow goes to step S14 that is implemented to carry out a
regenerative cooperative control.
[0238] When it is judged that the control system suffers from the
failure, namely, when a positive judgment (YES) is obtained in step
S13, the control flow goes to step S15 in which supply of the
electric current to the solenoids of all the electromagnetic valves
is stopped so that all the electromagnetic valves are placed in the
respective original positions. Further, the pump motor 92 is kept
inactivated.
[0239] When it is judged that there is a possibility of the fluid
leakage, namely, when a positive judgment (YES) is obtained in step
S12, the control flow goes to step S16 in which the hydraulic
pressure in the master cylinder 62 is supplied to the brake
cylinders 42 for the front left and right wheels 2, 4 while the
hydraulic pressure controlled by the output hydraulic-pressure
control valve device 178 is supplied to the brake cylinders 52 for
the rear left and right wheels 46, 48. It is rare that the control
system suffers from the failure and also there is a possibility of
the fluid leakage. Therefore, when it is judged that there is a
possibility of the fluid leakage, it is regarded that the control
system functions normally thereby making it possible to control the
electromagnetic valves and to activate the pump motor 92.
[0240] In the event of failure of the electric system, no electric
current is supplied to the brake system so that the electromagnetic
valves are returned to their original positions and the pump motor
92 is kept inactivated. That is, in the event of failure of the
electric system, the brake system is placed in the same state as in
the event of failure of the control system.
[0241] Further, in the present embodiment, the automatic brake is
inhibited from being carried out, when it is regarded that the
control system fails and when it is regarded that there is a
possibility of fluid leakage.
[0242] 1) In Case of Normality of System
[0243] To the brake cylinders 42, 52 for the four wheels 4, 2, 48,
46, the controlled hydraulic pressure (i.e., fluid pressurized by
the pump) is supplied from the power hydraulic pressure source 64,
so that the regenerative cooperative control is in principle
executed.
[0244] The regenerative cooperative control is executed for
equalizing an actual total braking torque to a total required
braking torque, wherein the actual total braking torque is a sum of
the regenerative braking torque applied to the driving wheels 2, 4
and a friction braking torque applied to the driven wheels 46, 48
as well as to the driving wheels 2, 4.
[0245] The total required braking torque corresponds to a braking
torque required by the vehicle operator, when the total required
braking torque is obtained based on values detected by the stroke
sensor 220 and the master-cylinder pressure sensor 222. The total
required braking torque corresponds to a braking torque required in
the traction control or vehicle stability control, when the total
required braking torque is obtained based on information supplied
from, for example, the following distance ECU 240 and the collision
avoidance ECU 242. Then, a required regenerative braking torque is
determined based on the above-described total required braking
torque and information which is supplied from the hybrid ECU 58 and
which contains data indicative of a generator-side upper limit
value and a storage-side upper limit value. The generator-side
upper limit value is an upper limit value of the regenerative
braking torque, which is dependent on, for example, number of
rotations of the electric motor 20, while the storage-side upper
limit value is an upper limit value of the regenerative braking
torque, which is dependent on, for example, a storage capacity of
the storage device 22. That is, the smallest one of the total
required braking torque (required value), generator-side upper
limit value and storage-side upper limit value is determined as the
required regenerative braking torque, and then information
representing the determined required regenerative braking torque is
supplied to the hybrid ECU 58.
[0246] The hybrid ECU 58 supplies information representing the
required regenerative braking torque, to the motor ECU 28. Then,
the motor ECU 28 supplies a control command to the conversion
device 26 such that the braking torque applied to the front left
and right wheels 2, 4 by the electric motor 20 is made equal to the
required regenerative braking torque. In this instance, the
electric motor 20 is controlled by the conversion device 26.
[0247] The motor ECU 28 supplies information representing
activation state of the electric motor 20 such as an actual number
of revolutions of the motor 20, to the hybrid ECU 58. In the hybrid
ECU 58, an actual regenerative braking torque is obtained based on
the actual activation state of the electric motor 20, and
information representing a value of the actual regenerative braking
torque is supplied to the brake ECU 56.
[0248] The brake ECU 56 determines a required hydraulic braking
torque based on, for example, a value obtained by subtracting the
actual regenerative braking torque from the total required braking
torque, and then controls valves such as the pressure-increasing
linear control valve 172 and pressure-reducing linear control valve
176, such that the brake cylinder hydraulic pressure becomes close
to a target hydraulic pressure that establishes the required
hydraulic braking torque.
[0249] During the regenerative cooperative control, in principle,
all the pressure holding valves 153FR, 153FL, 153RR, 153RL provided
for the respective four wheels 4, 2, 48, 46 are placed in the open
states while all the pressure reducing valves 156FL, 156FR, 156RL,
156RR provided for the respective four wheels 4, 2, 48, 46 are
placed in the closed states, as shown in FIG. 6. Further, the
master-cylinder cut-off valves 194FR, 194FL are placed in the
closed states, the simulator controlling valve 202 is placed in the
open state, and the pressure increasing mechanism cut-off valve 192
is placed in the closed state. With the common passage 152 being
isolated from the pressure increasing mechanism 100, and with the
brake cylinders 42FR, 42FL provided for the front right and left
wheels 4, 2 being isolated from the master cylinder 62, the
pressure-increasing linear control valve 172 and the
pressure-reducing linear control valve 176 are controlled so as to
control hydraulic pressure, and the controlled hydraulic pressure
is supplied to the common passage 152 and the brake cylinders 42,
52 provided for the respective four wheels.
[0250] In this state, if a braking slip of the wheels 2, 4, 46, 48
is excessively large so as to satisfy an anti-lock control starting
condition, the pressure holding valves 153 and pressure reducing
valves 156 are opened or closed independently of one another
whereby the hydraulic pressure in each of the brake cylinders 42,
52 is controlled, so that a slipping state of each of the front
right, front left, rear right and rear left wheels 4, 2, 48, 46 is
optimized.
[0251] Further, in a case where the hydraulic brake system is
installed on a vehicle which is not provided with the electric
drive device 6, i.e., on a vehicle in which the regenerative
cooperative control is not executed, the output hydraulic-pressure
control valve device 178 is controlled such that the hydraulic
braking torque is made equal to the total required braking
torque.
[0252] 2) In Case of Failure of Control System
[0253] (In Case of Failure of Electric System)
[0254] As shown in FIG. 7, all the electromagnetic valves are
placed back in the respective original positions.
[0255] The pressure-increasing linear control valve 172 and the
pressure-reducing linear control valve 176 are placed in the closed
states, by not supplying the electric current to the solenoids 186,
whereby the power hydraulic pressure source 64 is isolated from the
common passage 152.
[0256] Further, since the pressure increasing mechanism cut-off
valve 192 is placed in the open state, the pressure increasing
mechanism 100 is in communication with the common passage 152.
[0257] Further, the pressure holding valves 153FR, 153RL are placed
in the closed states while the pressure holding valves 153FL, 153RR
are placed in the open states, so that the brake cylinders 42FL,
52RR provided for the front left and rear right wheels 2, 48 are in
communication with the common passage 152 while the brake cylinders
42FR, 52RL provided for the front right and rear left wheels 4, 46
are isolated from the common passage 152.
[0258] The hydraulic pressures are generated in the pressurizing
chambers 70, 72 of the master cylinder 62, by operation of the
brake pedal 60.
[0259] The hydraulic pressure generated in the pressurizing chamber
72 is supplied to the pressure increasing mechanism 100 whereby the
pressure increasing mechanism 100 is activated. By forward movement
of the stepped piston 104, the small diameter chamber 112 is
isolated from the large diameter chamber 110 whereby the hydraulic
pressure in the small diameter chamber 112 is increased. The valve
opening member 125 is moved forwardly whereby the high-pressure
supply valve 116 is placed in the open state. Further, the highly
pressurized working fluid is supplied from the accumulator 66 to
the high pressure chamber 114 via the high-pressure-side check
valve 132, and is then supplied to the small diameter chamber 112.
The hydraulic pressure (servo pressure) in the small diameter
chamber 112 is made higher than the hydraulic pressure in the
master cylinder 62 (namely, the brake operating force is boosted),
and is supplied to the common passage 152 via the pressure
increasing mechanism cut-off valve 192 placed in the open state and
then supplied to the brake cylinders 42FL, 52RR provided for the
front left and rear right wheels 2, 48 via the pressure holding
valves 153FL, 153RR.
[0260] In this instance, since the master-cylinder cut-off valve
194FL provided for the front left wheel 2 is placed in the closed
state, it is possible to prevent the servo pressure supplied to the
brake cylinder 42FL, from flowing out to the master cylinder 62.
Therefore, the hydraulic brake 40FL can be activated
satisfactorily.
[0261] The pump device 65 remains inactivated so that the hydraulic
pressure in the accumulator 66 is reduced eventually. When the
hydraulic pressure in the accumulator 66 has become not higher than
the hydraulic pressure in the high pressure chamber 114, the flow
of the working fluid between the accumulator 66 and the high
pressure chamber 114 is inhibited whereby the forward movement of
the stepped piston 104 is inhibited. Further, in this instance,
there is a case where the forward movement of the stepped piston
104 is inhibited by the contact of the stepped piston 104 with the
above-described stopper. Thus, the hydraulic pressure in the small
diameter chamber 112 is not further increased so that the
mechanical pressure-increasing device 134 cannot exhibit a boosting
performance.
[0262] Meanwhile, when the hydraulic pressure in the pressurizing
chamber 72 of the master cylinder 62 has become higher than the
hydraulic pressure in the small diameter chamber 112, as a result
of increase of the operating force applied to the brake pedal 60,
the hydraulic pressure is supplied from the pressurizing chamber 72
to the small diameter chamber 112 (i.e., an output side portion of
mechanical pressure-increasing device 134) via the
pressure-increasing-device-bypass passage 136 and the manual-side
check valve 138, and also to the brake cylinders 42FL, 52RR
provided for the front left and rear right wheels 2, 48 via the
pressure increasing mechanism cut-off valve 192 and the pressure
holding valves 153FL, 153RR.
[0263] In this instance, the hydraulic pressure of the pressurizing
chamber 72 of the master cylinder 62 is supplied to the brake
cylinders 42FL, 52RR provided for the front left and rear right
wheels 2, 48, while not being boosted.
[0264] Further, since the pressure holding valves 153FR, 153RL are
placed in the closed states, the hydraulic pressure of the
pressurizing chamber 72 is inhibited from being supplied to the
brake cylinders 42FR, 52RL provided for the front right and rear
left wheels 4, 46.
[0265] A maximum amount of the working fluid suppliable from the
pressurizing chamber 72 as a chamber of the master cylinder 62 is
limited. Therefore, if the working fluid is to be supplied to a
large number of the brake cylinders, there could be a problem that
the hydraulic pressure in each of the bake cylinders cannot be
sufficiently increased. Moreover, a pressure receiving area of a
piston of each of the brake cylinders 42 for the front wheels is
larger than a pressure receiving area of a piston of each of the
brake cylinders 52 for the rear wheels. Therefore, the hydraulic
pressure in each of the front-wheel brake cylinders 42 and the
hydraulic pressure in each of the rear-wheel brake cylinders 52 are
to be equalized to each other, the working fluid is consumed more
in each front-wheel brake cylinder 42 than in each rear-wheel brake
cylinder 52.
[0266] Thus, there would be a risk of shortage of the braking force
in an arrangement in which the hydraulic pressure of the
pressurizing chamber 72 is supplied to the brake cylinders 42FL,
42FR provided for the front left and right wheels 2, 4.
[0267] On the other hand, it might be possible to employ an
arrangement in which the hydraulic pressure of the pressurizing
chamber 72 is supplied to the brake cylinders provided for two
wheels located in respective positions of the same side in a
lateral direction of the vehicle, for example, to the brake
cylinders 42FL, 52RL provided for the front left and rear left
wheels 2, 46. However, in this arrangement, there would be a risk
of generation of a yaw moment.
[0268] In the present embodiment in which the hydraulic pressure of
the pressurizing chamber 72 of the master cylinder 62 is supplied
to the brake cylinders provided for two wheels located in
respective positions diagonal to each other, i.e., to the brake
cylinders 42FL, 52RR provided for the front left and rear right
wheels 2, 48, it is possible to cause the two hydraulic brakes
40FL, 50RR to be satisfactorily activated, while restraining
generation of a yaw moment.
[0269] Meanwhile, to the brake cylinder 42FR provided for the front
right wheel 4, the hydraulic pressure is supplied from the
pressurizing chamber 70 of the master cylinder 62 via the master
master-cylinder cut-off valve 194FR that is placed in the open
state.
[0270] To the brake cylinder 52RL provided for the rear left wheel
46, no hydraulic pressure is supplied.
[0271] Thus, in the present embodiment, in the event of failure of
the control system or failure of the electric system, the hydraulic
pressures of the pressure increasing mechanism 100 and the master
cylinder 62 are supplied to the brake cylinders 42FL, 42FR, 52RR
provided for the three wheels. Consequently, a total brake force
applied to an entirety of the vehicle can be made larger than in an
arrangement in which the hydraulic pressure is supplied to the
brake cylinders provided for the two wheels.
[0272] Further, as long as the pressure increasing mechanism 100 is
being activated, the servo pressure is supplied to the front left
wheel 2, the master cylinder pressure is supplied to the front
right wheel 4 and the servo pressure is supplied to the rear right
wheel 48, so that a difference between the braking force applied to
a left-side portion of the vehicle and the braking force applied to
a right-side portion of the vehicle is made small whereby
generation of a yaw moment can be further restrained.
[0273] 3) In Case of Detection of Possibility of Fluid Leakage
[0274] As shown in FIG. 8, the pressure holding valves 153FR, 153FL
provided for the front right and left wheels 4, 2 are placed in the
closes states while the pressure holding valves 153RR, 153RL
provided for the rear right and left wheels 48, 46 are placed in
the open states. Further, the master-cylinder cut-off valves 194FR,
194FL are placed in the open states, the pressure increasing
mechanism cut-off valve 192 is placed in the closed state and the
simulator controlling valve 202 is placed in the closed state.
Further, all the pressure reducing valves 156 are placed in the
closed states. As described above, the hydraulic pressure of the
master cylinder 62 is supplied to the brake cylinders 42FL, 42FR
provided for the front left and right wheels 2, 4 while the
hydraulic pressure of the pump device 65 is supplied to the brake
cylinders 52RL, 52RR of the rear left and right wheels 46, 48.
[0275] Since the pressure holding valves 153FR, 153FL provided for
the front right and left wheels 4, 2 are placed in the closes
states, the brake cylinders 42FR, 42FL provided for the front right
and left wheels 4, 2 are isolated from each other, and are isolated
from the brake cylinders 52RR, 52RL provided for the rear right and
left wheels 48, 46. Thus, the brake cylinder for each front wheel
and the brake cylinder for each rear wheel are isolated from each
other, and the brake cylinders provided for the front left and
right wheels 2, 4 are isolated from each other. That is, three
brake lines (consisting of a brake line 250FL including the brake
cylinder 42FL provided for the front left wheel 2, a brake line
250FR including the brake cylinder 42FR provided for the front
right wheel 4 and a brake line 250R including the brake cylinders
52RL, 52RR provided for the rear left and right wheels 46, 48) are
isolated from one another. Consequently, even if one of the three
brake lines 250FL, 250FR, 250R suffers from the fluid leakage, the
other brake lines are not influenced by the fluid leakage taking
place in the one of the three brake lines.
[0276] Further, since the pressure increasing mechanism cut-off
valve 192 is placed in the closed state, it is possible to prevent
the working fluid supplied to the common passage 152 from the power
hydraulic pressure source 64, from flowing out to the pressure
increasing mechanism 100. In the present embodiment, the presence
of possibility of fluid leakage is detected, but it is not
specified which part of the brake system suffers from the fluid
leakage. In a case when the fluid leakage takes place in the brake
line 250FL, since the highly-pressurized hydraulic pressure cannot
be supplied to the large diameter chamber 110, the pressure
increasing mechanism 100 is kept inactivated. The stepped piston
104 is positioned in the reverse end position whereby the small
diameter chamber 112 and the large diameter chamber 110 are in
communication with each other via the communication passage 130. In
this instance, if the pressure increasing mechanism cut-off valve
192 were in the open state, the common passage 152 and the
pressurizing chamber 72 would be in communication with each other
via the communication passage 130, thereby causing a risk of flow
of the hydraulic pressure from the common passage 152 back to the
pressurizing chamber 72. However, by placing the pressure
increasing mechanism cut-off valve 192 in the closed state, it is
possible to satisfactorily prevent the working fluid from flowing
out from the common passage 152 toward the master cylinder 62 and
accordingly to supply the controlled pressure to the brake
cylinders 52RL, 52RR provided for the rear left and right wheels
46, 48.
[0277] In the present embodiment, the brake line 250 includes the
brake cylinder 42FR, master cylinder passage 76, pressurizing
chamber 70 and reservoir chamber 80. The brake line 250FL includes
the brake cylinder 42FL, master cylinder passage 74, pressurizing
chamber 72 and reservoir chamber 82. The brake line 250R includes
the brake cylinders 52RL, 52RR, individual passages 150RL, 150RR,
power hydraulic pressure source 64 and reservoir chamber 84.
[0278] 4) In Case of Release of Hydraulic Brake
[0279] Upon release of the brake operation, all the electromagnetic
valves are placed in the original positions, as shown in FIG. 2,
since electric current is not supplied to the solenoids of the
electromagnetic valves. Further, in the pressure increasing
mechanism 100, the stepped piston 104 is returned to the reverse
end position whereby the large diameter chamber 110 and the small
diameter chamber 100 are brought into communication with each other
via the communication passage 130.
[0280] The hydraulic pressure of the brake cylinder 42FR provided
for the front right wheel 4 is returned to the master cylinder 62
and the reservoir 78 via the master-cylinder cut-off valve 194FR
that is placed in the open state. The hydraulic pressure of the
brake cylinder 42FL provided for the front right wheel 2 is
returned to the master cylinder 62 and the reservoir 78 via the
pressure holding valve 153FL (that is placed in the open state),
pressure increasing mechanism cut-off valve 192 (that is placed in
the open state) and communication passage 130. The hydraulic
pressure of the brake cylinder 52RR provided for the rear right
wheel 48 is returned to the reservoir 78 via the pressure holding
valve 153RR, pressure increasing mechanism cut-off valve 192 and
pressure increasing mechanism 100. The hydraulic pressure of the
brake cylinder 52RL provided for the rear left wheel 46 is returned
to the reservoir 78 via the pressure reducing valve 156RL that is
placed in the open state.
[0281] The pressure holding valve 153RL is constituted by a
normally-closed electromagnetic valve, for inhibiting supply of the
working fluid from the master cylinder 62 and the pressure
increasing mechanism 100 to the brake cylinder 52RL provided for
the rear left wheel 46 in the event of failure of the control
system (failure of the electric system). Therefore, upon release of
the brake operation, the brake cylinder 52RL becomes isolated from
the common passage 152 so that the working fluid cannot be returned
from the brake cylinder 52RL to the master cylinder 62 via the
pressure increasing mechanism 100. However, since the pressure
reducing valve 156RL is constituted by a normally-open
electromagnetic valve, the working fluid can be returned from the
brake cylinder 52RL to the reservoir 78 via the pressure reducing
valve 156RL. Further, if all of the pressure reducing valve 156
were constituted by normally-open electromagnetic valves, it would
be necessary to keep the electric current supplied to the solenoids
during activations of the hydraulic brakes 40, 50, thereby causing
a problem of large consumption of electric power. In the present
embodiment, since only the pressure reducing valve 156RL among the
pressure reducing valves 156 is constituted by a normally-open
electromagnetic valve, it is possible to restrain increase of
consumption of electric power.
[0282] As described above, in the present embodiment, the supply of
the hydraulic pressure to the brake cylinders 42, 52 are controlled
based on results of the initial checks.
[0283] In case of failure of the control system (failure of the
electric system), it is possible to supply the hydraulic pressure
higher than the hydraulic pressure of the master cylinder 62, to
the brake cylinders 42FL, 52RR, by activation of the pressure
increasing mechanism 100. Further, the hydraulic pressure of the
master cylinder 62 is supplied to the brake cylinder 42FR provided
for the front right wheel 4. Thus, in case of failure of the
electric system, the hydraulic brakes 40FL, 40FR, 50RR provided for
the three wheels can be activated. Consequently, as compared with
an arrangement in which the brake cylinders provided for two wheels
are activated, it is possible to further satisfactorily avoid
insufficiency of the braking force. Further, since the servo
pressure is supplied to the brake cylinders for the two wheels
located in the respective positions diagonal to each other, it is
possible to restrain generation of a yaw moment.
[0284] In case of detection of possibility of fluid leakage, the
three brake lines 250FL, 250FR, 250R are isolated from one another.
Therefore, even if the fluid leakage occurs in any one of the three
brake lines 250FL, 250FR, 250R, it is possible to satisfactorily
avoid the other brake lines from being influenced by the fluid
leakage occurring in the one of the brake lines. Further, the
hydraulic brakes can be reliably activated in the brake lines that
do not suffer from the fluid leakage.
[0285] Further, in the present embodiment, the pressure holding
valve 153FL functions as a right/left cut-off valve and each of the
pressure holding valves 153FL, 153FR functions as a front/rear
cut-off valve, thereby eliminating necessity of provisions of
valves serving exclusively as the front/rear cut-off valve and
right/left cut-off valve and accordingly making it possible to
reduce the cost.
[0286] In the hydraulic brake system constructed as described
above, a pressure-supply control device is constituted by, for
example, portions of the brake ECU 56 which are assigned to store
and execute the hydraulic-pressure-supply control program
represented by the flow chart of FIG. 5. The pressure-supply
control device serves also as an electromagnetic-valve controlling
portion. It can be also considered that a communication-cut-off
control device is constituted by, for example, by portions of the
brake ECU 56 which are assigned to store and implement step S16 of
the hydraulic-pressure-supply control program.
[0287] Further, an output hydraulic pressure control device is
constituted by, for example, the output hydraulic-pressure control
valve device 178 and portions of the brake ECU 56 which are
assigned to store and implement steps S14 and S16 of the
hydraulic-pressure-supply control program.
[0288] Further, the master cylinder passage 74, individual passage
150FL, pressure holding valve 153FL, master-cylinder cut-off valve
194FL and brake cylinder 42FL correspond to a first
manual-pressure-source passage, a first individual passage, a first
valve, a first manual-pressure-source cut-off valve and a first
brake cylinder, respectively. The master cylinder passage 76,
individual passage 150FR, pressure holding valve 153FR,
master-cylinder cut-off valve 194FR and brake cylinder 42FR
correspond to a second manual-pressure-source passage, a second
individual passage, a second valve, a second manual-pressure-source
cut-off valve and a second brake cylinder, respectively. Further,
each of the pressure holding valves 153FL, 153FR, 153RL, 153RR
serves also as a pressure-increasing control valve.
[0289] Moreover, a pressure supply passage is constituted by, for
example, the common passage 152 and individual passage 150.
[0290] Further, a fluid-leakage possibility detecting device is
constituted by, for example, portions of the brake ECU 56 which are
assigned to store and implement step S3 of the initial-check
program.
Embodiment 2
[0291] FIG. 9 shows a diagram of a hydraulic circuit of the
hydraulic brake system according to Embodiment 2 of the present
invention. In the following description, the same reference sings
will be used to identify constructional elements identical with
those in the hydraulic circuit of the hydraulic brake system of
Embodiment 1, and description of these elements will be omitted.
For example, the brake ECU 56 executes controls in the same manners
as in Embodiment 1.
[0292] In Embodiment 2, the brake cylinders 52RL, 52RR provided for
the rear left and right wheels 46, 48 are connected to the common
passage 310 via a single individual passage 312, so that the
hydraulic pressures in the brake cylinders 52RL, 52RR of the rear
left and right wheels 46, 48 are controlled commonly. The
individual passage 312 is provided with a common pressure holding
valve 314 that is constituted by a normally-closed electromagnetic
valve. A brake-cylinder-side check valve 316 is disposed in
parallel with the pressure holding valve 314. The check valve 316
allows flow of the working fluid in a direction away from the brake
cylinders 52RL, 52RR toward the common passage 310, and inhibits
flow of the working fluid in the opposite direction away from the
common passage 310 toward the brake cylinders 52RL, 52RR.
[0293] Further, the brake cylinders 42FL, 42FR provided for the
front left and right wheels 2, 4 are connected to the common
passage 310 via respective individual passages 320FL, 320FR each of
which is not provided with a pressure holding valve. The master
cylinder passages 74, 76 are connected to the respective individual
passages 320FL, 320FR, and are provided with respective
master-cylinder cut-off valves 324FL, 324FR. The master-cylinder
cut-off valve 324FL is constituted by a normally-closed
electromagnetic valve while the master-cylinder cut-off valve 324FR
is constituted by a normally-open electromagnetic valve.
[0294] Further, a front/rear cut-off valve 330 is disposed between
a connected portion of the common passage 310 (at which the common
passage 310 is connected to the individual passage 312) and a
connected portion of the common passage 310 (at which the common
passage 310 is connected to the servo pressure passage 190). A
right/left cut-off valve 332 is disposed between connected portions
of the common passage 310 at which the common passage 310 is
connected to the respective individual passages 320FL, 320FR.
[0295] Each of the front/rear cut-off valve 330 and right/left
cut-off valve 332 is constituted by a normally-open electromagnetic
valve.
[0296] Although the right/left cut-off valve 332 is disposed in the
common passage 310 in the hydraulic brake circuit shown in FIG. 9,
this valve 332 may be disposed in a portion of the individual
passage 320FL which is located between the master cylinder passage
74 and the common passage 310 or disposed in a portion of the
individual passage 320FR which is located between the master
cylinder passage 76 and the common passage 310. Further, although
the front/rear cut-off valve 330 is disposed between the connected
portion of the common passage 310 (at which the common passage 310
is connected to the individual passage 312) and the connected
portion of the common passage 310 (at which the common passage 310
is connected to the servo pressure passage 190), this valve 330 may
be disposed between a connected portion of the common passage 310
(at which the common passage 310 is connected to the individual
passage 320FL) and the connected portion of the common passage 310
(at which the common passage 310 is connected to the servo pressure
passage 190).
[0297] There will be described activation of the hydraulic brake
system that is constructed as described above.
[0298] 1) In Case of Normality of Hydraulic Brake System
[0299] As shown in FIG. 10, the hydraulic pressure controlled by
the output hydraulic-pressure control valve device 178 is supplied
to the common passage 310, with the pressure increasing mechanism
100 isolated from the common passage common passage 310 and the
brake cylinders 42FL, 42FR of the front left and right wheels 2, 4
isolated from the master cylinder 62.
[0300] Further, the pressure holding valve 314 provided for the
rear right and left wheels 46, 48 is placed in the open state, and
the front/rear cut-off valve 330 and the right/left cut-off valve
332 are placed in the open states, so that the controlled pressure
is supplied to all of the brake cylinders 42, 52.
[0301] 2) In Case of Failure of Control System
[0302] (In Case of Failure of Electric System)
[0303] As shown in FIG. 11, all the electromagnetic valves are
placed back in the respective original positions. The servo
pressure outputted from the pressure increasing mechanism 100 is
supplied to the common passage 310. In this instance, since the
pressure holding valve 314 provided for the rear left and right
wheels 46, 48 is constituted by the normally-closed electromagnetic
valve, the servo pressure is supplied to the brake cylinders 42FL,
42FR provided for the front left and right wheels 2, 4.
[0304] Further, since the master-cylinder cut-off valve 324FR is
placed in the open state, the hydraulic pressure outputted from the
pressure increasing mechanism 100 is supplied to the pressurizing
chamber 70 as long as the outputted hydraulic pressure is being
higher than the hydraulic pressure of the master cylinder 62. As a
result of the supply of the outputted hydraulic pressure to the
pressurizing chamber 70, the hydraulic pressure to in the
pressurizing chamber 70 is increased whereby the force applied to
the pressurizing piston 69 is increased and accordingly the
hydraulic pressure in the pressurizing chamber 72 is increased.
Thus, the pressure increasing mechanism 100 can be activated by the
increased hydraulic pressure whereby the hydraulic pressure
outputted from the pressure increasing mechanism 100 can be
increased. It is therefore possible to further increase the
hydraulic pressures in the brake cylinders 42FL, 42FR of the front
left and right wheels 2, 4.
[0305] When the pressure of the working fluid stored in the
accumulator 66 becomes so low that the hydraulic pressure in the
pressurizing chamber 72 becomes higher than the hydraulic pressure
outputted from the pressure increasing mechanism 100, the hydraulic
pressure in the master cylinder 62 is supplied mainly to the brake
cylinder 42FL of the front left wheel 2 via the manual-side check
valve 138. Further, the hydraulic pressure in the pressurizing
chamber 70 of the master cylinder 62 is supplied to mainly the
brake cylinder 42FR of the front right wheel 4. Thus, the hydraulic
pressures in the pressurizing chambers 72, 70 are supplied to the
respective brake cylinders 42FL, 42FR provided for the respective
front left and right wheels 2, 4, whereby the hydraulic brakes
40FL, 40FR can be satisfactorily activated.
[0306] Further, since the hydraulic pressures in the brake
cylinders 40FL, 40FR of the respective front left and right wheels
2, 4 become substantially equal in magnitude to each other, a yaw
moment is unlikely to be generated.
[0307] 3) In Case of Detection of Possibility of Fluid Leakage
[0308] As shown in FIG. 12, the pressure increasing mechanism
cut-off valve 192, right/left cut-off valve 332 and front/rear
cut-off valve 330 are placed in the closed states. Further, the
pressure holding valve 314 is placed in the open state, and the
master-cylinder cut-off valves 324FL, 324FR are placed in the open
states.
[0309] The hydraulic pressure of the power hydraulic pressure
source 64 is controlled and supplied to the brake cylinders 52RL,
52RR provided for the rear left and right wheels 46, 48, while the
hydraulic pressure of the master cylinder 62 is supplied to the
brake cylinders 42FL, 42FR provided for the front left and right
wheels 2, 4. In this instance, since the right/left cut-off valve
332 and front/rear cut-off valve 330 are placed in the closed
states, three brake lines, which consist of a brake line 350FL
including the brake cylinder 42FL, a brake line 350FR including the
brake cylinder 42FR and a brake line 350R including the brake
cylinders 52RL, 52RR, are isolated from one another. Therefore,
even if one of the three brake lines 350FL, 350FR, 350R suffers
from the fluid leakage, the other brake lines are not influenced by
the fluid leakage taking place in the one of the three brake lines.
Further, the hydraulic brakes can be reliably activated in the
brake lines that do not suffer from the fluid leakage.
[0310] In the present embodiment, since the right/left cut-off
valve 332 is disposed in a portion of the common passage 310 which
portion is located between the connected portion of the common
passage 310 (at which the common passage 310 is connected to the
servo pressure passage 190) and the brake cylinder 42FR of the
front right wheel 4, the pressure increasing mechanism cut-off
valve 192 does not necessarily have to be placed in the closed
state. This is because when the right/left cut-off valve 332 and
front/rear cut-off valve 330 are placed in the closed states, the
pressure increasing mechanism 100 is in communication with only the
brake cylinder 42FL of the front left wheel 2 while being isolated
from the other brake lines 350FR, 350R.
[0311] 4) In Case of Release of Hydraulic Brake
[0312] All the electromagnetic valves are placed back in the
original positions, as shown in FIG. 9. The working fluid in the
brake cylinder 42FR of the front right wheel 4 is returned to the
master cylinder 62 via the master cylinder passage 76, while the
working fluid in the brake cylinder 42FL of the front left wheel 2
is returned to the master cylinder 62 via the pressure increasing
mechanism 100. The working fluid in the brake cylinders 52RL, 52RR
of the rear left and right wheels 46, 48 is returned to the master
cylinder 62, via the brake-cylinder-side check valve 316,
front/rear cut-off valve 330 (that is placed in the open state),
common passage 310 and pressure increasing mechanism 100, or via
the front/rear cut-off valve 330 (that is placed in the open
state), right/left cut-off valve 332 (that is placed in the open
state) and master-cylinder cut-off valve 324.
[0313] Thus, in the present embodiment, the brake-cylinder-side
check valve 316 is disposed in parallel with the pressure holding
valve 314 which is provided for the rear wheels 46, 48 and which is
constituted by the normally-closed electromagnetic valve.
Therefore, by inhibiting the working fluid from being supplied to
the brake cylinders 52 of the rear wheels 46, 48 in the event of
failure of the electric system, it is possible to assure the
braking force and to cause the working fluid to be reliably
returned from the brake cylinders 52 of the rear wheels 46, 48 upon
release of the hydraulic brake.
[0314] In the present embodiment, the individual passage 312
corresponds to a third individual passage, and the pressure holding
valve 314 corresponds to a third valve.
[0315] The pressure holding valve 314 may be adapted to function as
a brake-side check valve. The pressure holding valve 314 is
constituted by the normally-closed electromagnetic valve, and has
the same construction as the pressure-increasing linear control
valve 172 and pressure-reducing linear control valve 176 that are
shown in FIG. 3. When the electric current is not being supplied to
the solenoid of the valve 314 with the valve 314 placed in the
closed state, the pressure-difference-based force F3 and the
biasing force F2 act on the valve body of the valve 314, wherein
the pressure-difference-based force F3 is generated based on a
difference between input and output sides of the valve 314, and the
biasing force F2 is generated by the spring of the valve 314. Where
the spring force of the valve 314 is adapted to generate a small
force as the biasing force F2, the valve 314 can be switched from
the closed state to the open state, when the hydraulic pressure in
the brake cylinder 52 becomes higher than the hydraulic pressure in
the common passage 310 so that the pressure-difference-based force
F3 becomes larger than the biasing force F2. Thus, by adapting the
spring of the valve 314 to generate the small biasing force, it is
possible to eliminate necessity of provision of the
brake-cylinder-side check valve 316 and accordingly to further
reduce the cost.
Embodiment 3
[0316] In the hydraulic brake system constructed according to
Embodiment 2, the electromagnetic valves are controlled to be
placed in the respective positions shown in FIG. 12 when the
possibility of fluid leakage is detected. However, the valves may
be controlled in a different manner.
[0317] There will be described how the right/left cut-off valve 332
and front/rear cut-off valve 330 are controlled upon detection of
possibility of presence of fluid leakage in a brake system
including a hydraulic brake system that is the same as that in
Embodiment 2.
[0318] It is preferable that the right/left cut-off valve 332 and
front/rear cut-off valve 330 are held in the closed states as long
as possible when the presence of possibility of fluid leakage is
detected. The fluid leakage does not necessarily occur even when
the presence of possibility of fluid leakage is detected. However,
it is preferable that, when one of the brake lines actually suffers
from the fluid leakage, the other brake lines are not influenced by
the fluid leakage taking place in the one of the three brake lines.
Since the right/left cut-off valve 332 and front/rear cut-off valve
330 are constituted by normally-open electromagnetic valves, it is
necessary to keep supplying electric current to their solenoids for
keeping them in the closed states. When the supply of the electric
current is made for a large length of time, there could be problems
such as increase of consumption of the electric power and an
excessive heating of the solenoids.
[0319] On the other hand, as long as the hydraulic pressure is not
applied to the brake lines 350FL, 350FR, 350R, even if the fluid
leakage actually takes place in one of the brake lines, the working
fluid flows little out from the brake line that suffers from the
fluid leakage so that the other brake lines are influenced little
by the fluid leakage.
[0320] In view of the above, in Embodiment 2, upon detection of
presence of the possibility of fluid leakage, the right/left
cut-off valve 332 and the front/rear cut-off valve 330 are, in
principle, held in the closed states, and are placed in the open
state by turning OFF the electric current supplied to the solenoids
when a predetermined valve-open allowing condition is satisfied
(namely, when it is not problematic that the cut-off valves 332,
330 are placed in the open states).
[0321] In other words, even upon detection of presence of the
possibility of fluid leakage, the cut-off valves 332, 330 are
placed in the closed states by turning ON the electric current
supplied to the solenoids, only when the valves 332, 330 are really
required to be placed in the closes states (namely, only when a
predetermined valve-closed allowing condition is satisfied). Thus,
it is possible to prevent the solenoids from being excessively
heated and accordingly to reduce consumption of the electric
power.
[0322] A) The right/left cut-off valve 332 and the front/rear
cut-off valve 330 can be controlled in accordance with a front/rear
cut-off valve & right/left cut-off valve control program which
is represented by a flow chart of FIG. 13 and which is executed at
a predetermined time interval.
[0323] This control program is initiated with step S61 that is
implemented to read result of detection of presence of possibility
of fluid leakage. When there is a possibility of fluid leakage,
step S62 is implemented to judge whether the brake switch 218 is in
the ON state. When the brake switch 218 is in the ON state, the
control flow goes to step S63 in which the right/left cut-off valve
332 and front/rear cut-off valve 330 are placed in the closed
states. When the brake switch 218 is placed in the OFF state, the
control flow goes to step S64 in which the cut-off valves 332, 330
are placed in the open states without supply of the electric
current to the solenoids. When the brake switch 218 is switched
from the OFF state to the ON state, the cut-off valves 332, 330 are
switched from the open states to the closed states.
[0324] During activations of the hydraulic brakes 40, 50 in the ON
state of the brake switch 218, it is preferable that the right/left
cut-off valve 332 and the front/rear cut-off valve 330 are placed
in the closed states while the three brake lines 350FL, 350FR, 350R
are isolated from one another so that, as in Embodiment 2, the
hydraulic pressure controlled by the output hydraulic-pressure
control valve device 178 can be supplied to the brake cylinders
52RL, 52RR provided for the rear left and right wheels 46, 48 while
the hydraulic pressure of the master cylinder 62 can be supplied to
the brake cylinders 42FL, 42FR provided for the front left and
right wheels 2, 4.
[0325] Where a regenerative cooperative control is inhibited from
being executed upon detection of presence of the possibility of
fluid leakage, it is considered that the hydraulic brakes 40, 50
are being activated when the brake switch 218 is in the ON
state.
[0326] In each of the right/left cut-off valve 332 and front/rear
cut-off valve 330, the heating of the solenoid can be retrained,
for example, by increasing number of turns of coil in the solenoid
and/or by controlling the electric current supplied to the
solenoid.
[0327] During inactivations of the hydraulic brakes 40, 50 in the
OFF state of the brake switch 218, the other brake lines are
influenced little by the fluid leakage even if the right/left
cut-off valve 332 and front/rear cut-off valve 330 are placed in
the open states. Therefore, when the brake switch 218 is placed in
the OFF state, the electric current supplied to the solenoids of
the cut-off valves 332, 330 is turned OFF whereby the valves 332,
330 are placed in the open states. Thus, it is possible to reduce
consumption of the electric power and to restrain heating of the
solenoids.
[0328] When there is no possibility of fluid leakage, a negative
judgment (NO) is obtained in step S61 so that steps S63 and S64 are
not implemented. That is, when there is no possibility of fluid
leakage, the right/left cut-off valve 332 and the front/rear
cut-off valve 330 are not controlled in accordance with this
front/rear cut-off valve & right/left cut-off valve control
program but are controlled in accordance with other program such as
the hydraulic-pressure-supply control program. Therefore, when it
is judged that there is no possibility of fluid leakage, it is
common that the cut-off valves 332, 330 are placed back into the
open states, but they are not necessarily placed back into the open
states immediately. For example, in a vehicle stability control or
a traction control, the right/left cut-off valve 332 is placed in
the closed state when the hydraulic pressure controlled by the
output hydraulic-pressure control valve device 178 is to be
supplied only to the brake cylinder 42FL of the front left wheel
2.
[0329] It is noted that step S62 may be implemented by judging
whether the hydraulic pressure detected by the brake-cylinder
pressure sensor 226 is equal to or higher than a judgment threshold
value, which is a value determined such that it can be regarded
that the hydraulic brakes 40, 50 are being activated when the
detected hydraulic pressure is not lower than this judgment
threshold value. With step S62 being thus implemented, the
right/left cut-off valve 332 and the front/rear cut-off valve 330
can be placed in the closed states, for example, also when the
automatic brake is being activated upon detection of presence of
the possibility of fluid leakage.
[0330] Further, the detection as to whether there is the
possibility of fluid leakage may be made not only when the initial
check is carried out but also when it is required. That is, the
detection as to whether there is the possibility of fluid leakage
may be made in step S61.
[0331] A communication-cut-off control device is constituted by,
for example, portions of the brake ECU 56 which are assigned to
store and execute the front/rear cut-off valve & right/left
cut-off valve control program shown in FIG. 13. The portions of the
brake ECU 56 include portions which are assigned to store and
implement steps S62 and S63 and which cooperate to constitute an
electromagnetic-valve closing control portion. The portions of the
brake ECU 56 further include portions which are assigned to store
and implement steps S62 and S64 and which cooperate to constitute
an electromagnetic-valve opening control portion. The
electromagnetic-valve closing control portion serves also as an
operation-based closing control portion.
[0332] Further, the right/left cut-off valve 332 corresponds to a
first communication shut-off valve while the front/rear cut-off
valve 330 corresponds to a second communication shut-off valve.
[0333] It can be also considered that the electromagnetic-valve
closing control portion corresponds to an electromagnetic-valve
closing hold portion and that the electromagnetic-valve opening
control portion corresponds to an electromagnetic-valve
compulsorily opening control portion.
[0334] B) The right/left cut-off valve 332 and the front/rear
cut-off valve 330 can be controlled also in accordance with a
control program which is represented by a flow chart of FIG.
14.
[0335] This control program is initiated with step S71 that is
implemented to read result of detection of presence of possibility
of fluid leakage. When there is a possibility of fluid leakage,
steps S72 and S73 are implemented to judge whether at least one of
the hydraulic pressures in the respective brake cylinders 42, 52 is
higher than a given pressure value and to judge whether an absolute
value of rate of change of at least one of the hydraulic pressures
in the respective brake cylinders 42, 52 is higher than a given
rate value. When a positive judgment (YES) is obtained in at least
one of steps S72 and S73, step S74 is implemented to place the
cut-off valves 332, 330 into the closed states. When a negative
judgment (NO) is obtained in each of steps S72 and S73, step S75 is
implemented to placed the cut-off valves 332, 330 into the open
states.
[0336] The above-described given pressure value may be a value
determined such that it can be regarded that, in the event of fluid
leakage, the working fluid is caused to leak out from a leakage
part (e.g., a part deteriorated in sealing performance) by at least
a given amount and accordingly the influence affecting the other
brake lines becomes problematic when the hydraulic pressure in the
brake cylinder is higher than the given pressure value. In this
sense, the given pressure value may be referred to as an
influence-based judgment threshold value.
[0337] The given pressure value may be higher than a pressure value
(activation-judgment threshold value) determined such that it can
be regarded that the hydraulic brakes 42, 52 are being activated
when the hydraulic pressures in the brake cylinders are higher than
the activation-judgment threshold value. In other words, even
during activations of the hydraulic brakes 42, 52, when the
hydraulic pressures in the brake cylinders 42, 52 are low, the
amount of fluid leakage is so small that the influence by the fluid
leakage is small, and accordingly it is not problematic that the
cut-off valves 332, 330 are placed in the open states. However,
when the hydraulic pressures are high, the influence by the fluid
leakage is large so that it is considered that the cut-off valves
332, 330 are highly required to be placed in the closed states.
[0338] When the absolute value of rate of change of the hydraulic
pressure in each of the brake cylinders 42, 52 is larger than the
given rate value, it is considered that the amount of fluid leakage
becomes large. Further, when the rate of increase of the brake
cylinder pressure is high, it can be considered that there is a
high possibility that the brake cylinder pressure becomes high.
Therefore, when the absolute value of rate of change of the brake
cylinder pressure is large, it is preferable that the right/left
cut-off valve 332 and the front/rear cut-off valve 330 are placed
in the closed states.
[0339] Further, when the right/left cut-off valve 332 and the
front/rear cut-off valve 330 are placed in the open states, it is
preferable that the master-cylinder cut-off valves 324FL, 34FR are
placed in the closed states.
[0340] In the present embodiment, a hydraulic-pressure-based
closing control portion is constituted by, for example, portions of
the brake ECU 56 which are assigned to store and implement steps
S72, S73 and S74.
[0341] It is noted that step S73 may be implemented by judging
whether there is a high possibility that the absolute value of rate
of change of the brake cylinder pressure becomes larger than the
given rate value. For example, when there is a high possibility
that the brake pedal 60 is to be operated, it can be considered
that there is a high possibility that the rate of increase of the
brake cylinder pressure becomes higher than the given rate
value.
[0342] C) The right/left cut-off valve 332 and the front/rear
cut-off valve 330 can be controlled also in accordance with a
control program which is represented by a flow chart of FIG.
15.
[0343] When there is a possibility of fluid leakage, steps S82 and
S83 are implemented to judge whether a running velocity of the
vehicle is equal to or lower than a given velocity value with the
ignition switch 234 being placed in the ON state and to judge
whether the acceleration switch 234 is placed in the OFF state with
the ignition switch 234 being placed in the ON state. The given
velocity value is a value determined such that it can be regarded
that the vehicle is being stopped when the running velocity is not
higher than the given velocity value. When a positive judgment
(YES) is obtained in at least one of steps S82 and S83, step S84 is
implemented to place the cut-off valves 332, 330 into the closed
states. When a negative judgment (NO) is obtained in each of steps
S82 and S83, step S85 is implemented to placed the cut-off valves
332, 330 into the open states. When the ignition switch 234 is
placed in the OFF state, or when the accelerator pedal is being
operated during running of the vehicle with the ignition switch 234
placed in the ON state, it is not considered problematic that the
cut-off valves 332, 330 are placed in the open states since there
is not a high possibility that the brake pedal 60 is to be operated
in such a case.
[0344] When the running velocity of the vehicle is not higher than
the given velocity value or when the accelerator pedal is not being
operated, it is preferable that the cut-off valves 332, 330 are
placed in the closed states since there is a high possibility that
the brake pedal 60 is to be operated in such a case. During
operation of the brake pedal 60, the rate of increase of the
hydraulic pressure in each of the brake cylinders 42 52 becomes
high so that the other brake lines are influenced much by the fluid
leakage. Therefore, it is preferable to place the cut-off valves
332, 330 into the closed states before the operation of the brake
pedal 60 is actually started.
[0345] When the brake pedal 60 is being actually operated, the
accelerator switch 324 is placed in the OFF state so that a
negative judgment (NO) is obtained in step S83 and step S84 is
implemented to place the right/left cut-off valve 332 and the
front/rear cut-off valve 330 into the closed states.
[0346] In the present embodiment, a vehicle-stop closing control
portion is constituted by, for example, portions of the brake ECU
56 which are assigned to store and implement steps S82 and S84, and
an operation-based closing control portion is constituted by, for
example, portions of the brake ECU 56 which are assigned to store
steps S82 through S84.
[0347] Since the right/left cut-off valve 332 and the front/rear
cut-off valve 330 are placed in the closed states also after the
brake pedal 60 has been released, it is preferable to place the
pressure-reducing linear control valve 176 in the open state for a
given length of time after release of the brake pedal 60, so as to
cause the hydraulic pressures of the brake cylinders 52RL, 52RR of
the rear wheels 46, 48 to be returned to the reservoir 78 via the
pressure-reducing linear control valve 176.
[0348] D) The right/left cut-off valve 332 and the front/rear
cut-off valve 330 can be controlled also in accordance with a
control program which is represented by a flow chart of FIG. 16. In
the present embodiment, when fluid leakage is detected, the cut-off
valves 332, 330 are, in principle, held in the closed states, but
are placed in the open states for a given length time after the
brake switch 218 has been placed from the ON state to the OFF state
because there is not a high possibility that the brake operation is
carried out again with the given length time after release of the
brake pedal. It is noted that the given length of time is a length
of time determined such that it can be thought that the brake
operation is unlikely to be performed within the given length of
time.
[0349] Step S91 is implemented to detect whether there is a
possibility of fluid leakage. When presence of the possibility of
fluid leakage is detected, step S92 is implemented to judge whether
a given length of time (e.g., about two seconds) has elapsed after
the brake switch 218 has been switched from the ON state to the OFF
state. Until the given length of time has elapsed, step S93 is
implemented to keep the cut-off valves 332, 330 in the open states.
When the given length of time has elapsed, step S94 is implemented
to place the cut-off valves 332, 330 into the closed states. That
is, even during the OFF state of the brake switch 218, the cut-off
valves 332, 330 are placed in the closed states, and held in the
closed states irrespective of whether the ignition switch 234 is
placed in the ON or OFF state.
[0350] In the present embodiment, an electromagnetic-valve closing
hold portion is constituted by, for example, portions of the brake
ECU 56 which are assigned to store and implement steps S91, S92 and
S94, and an electromagnetic-valve compulsorily opening control
portion is constituted by, for example, portions of the brake ECU
56 which are assigned to store and implement steps S92 and S93.
Further, it can be considered that an operation-based closing
control portion is constituted by, for example, the portions of the
brake ECU 56 which are assigned to store and implement steps S92
and S93.
[0351] E) The right/left cut-off valve 332 and the front/rear
cut-off valve 330 can be controlled also in accordance with a
control program which is represented by a flow chart of FIG. 17. In
the present embodiment, in case of detection of fluid leakage, the
cut-off valves 332, 330 are held in closed states when the ignition
switch 234 is placed in the ON state, and are held in the open
states when the ignition switch 234 is placed in the OFF state.
[0352] Step S95 is implemented to detect whether there is a
possibility of fluid leakage. When presence of the possibility of
fluid leakage is detected, step S96 is implemented to judge whether
the ignition switch 234 is placed in the ON state. When the
ignition switch 234 is placed in the ON state, step S97 is
implemented to place the cut-off valves 332, 330 in the closed
states. When the ignition switch 234 is placed in the OFF state,
step S98 is implemented to place the cut-off valves 332, 330 in the
open states.
[0353] In the present embodiment, a switch-ON closing control
portion is constituted by, for example, portions of the brake ECU
56 which are assigned to store and implement steps S96 and S97.
[0354] It is noted that the right/left cut-off valve 332 and the
front/rear cut-off valve 330 may be always held in closed states
irrespective of whether the ignition switch 234 is in the ON or OFF
state.
[0355] Further, when the brake switch 218 is placed in the OFF
state with the right/left cut-off valve 332 and front/rear cut-off
valve 330 being held in the closed states over a predetermined
maximum length of time (that is allowable for preventing heat
generation), the cut-off valves 332, 330 may be held in the open
states for a predetermined length of time for cooling the
solenoids, so that it is possible to satisfactorily restrain
heating of the solenoids and to reduce consumption of the electric
power.
[0356] Moreover, the right/left cut-off valve 332 and the
front/rear cut-off valve 330 may be controlled also in accordance
with combination of a part or all of at least two of the
above-described five control programs.
[0357] Further, the right/left cut-off valve 332 and the front/rear
cut-off valve 330 may be controlled in accordance with respective
programs that are other than each other. Further, the right/left
cut-off valve 332 and the front/rear cut-off valve 330 may be
alternately placed in the open state when a predetermined condition
or conditions are satisfied.
Embodiment 4
[0358] The brake circuit may be constructed as shown in FIG.
18.
[0359] In the brake circuit according to the present embodiment,
each of individual hydraulic-pressure control portions 360FL, 360FR
is disposed on a midway of a corresponding one of the individual
passages 320FL, 320FR provided for the respective front left and
right wheels 2, 4, so as to control the hydraulic pressure in a
corresponding one of the brake cylinders 42FL, 42FR. Each of the
individual hydraulic-pressure control portions 360FL, 360FR may be
constituted by at least one electromagnetic valve such as the
pressure holding valve 153 and pressure reducing valve 156 included
in the hydraulic brake system of Embodiment 1, or the
pressure-increasing linear control valve 172 and pressure-reducing
linear control valve 176 included in the hydraulic brake system of
Embodiment 1. With provisions of the individual hydraulic-pressure
control portions 360FL, 360FR, it is possible to finely control the
hydraulic pressures in the brake cylinders 42FL, 42FR.
[0360] It is noted that the pressure increasing mechanism 100 and
the output hydraulic-pressure control valve device 178 are not
essential. Further, the power hydraulic pressure source 64 may be
employed exclusively to activate the pressure increasing mechanism
100.
[0361] Further, the present invention can be carried out also in
modes in which two or more of Embodiments 1, 2 and 3 are combined.
For example, in a mode in which Embodiments 1 and 2 are combined,
the brake hydraulic pressure circuit may be construed such that (i)
the pressure holding valves 153FL, 153FR and the pressure reducing
valves 156FL, 156FR are provided for the brake cylinders 42FL, 42FR
of the front left and right wheels while the pressure holding valve
314 is provided commonly for the brake cylinders 52RL, 52RR of the
rear left and right wheels or (ii) the pressure holding valve 332
is provided for the brake cylinder 42FR of the front right wheel
while the pressure holding valves 153RL, 153RR and the pressure
reducing valves 156RL, 156RR are provided for the brake cylinders
52RL, 52RR of the rear left and right wheels. Further, the controls
executed in Embodiment 3 may be applied to the brake hydraulic
pressure circuit of Embodiment 1. In this case, both of the
pressure holding valves 153FL, 153FR or the normally-open pressure
holding valve 153FR is subjected to the controls.
[0362] Moreover, the present invention can be carried out in not
only the above-described modes but also in other modes of various
modifications and improvements that will be made based on knowledge
of a person skilled in the art.
DESCRIPTION OF REFERENCE SIGNS
[0363] 40, 50: hydraulic brake 42, 52: brake cylinder 54:
hydraulic-pressure controlling portion 56: brake ECU 60: brake
pedal 62: master cylinder 64: power hydraulic pressure source 66:
accumulator 70, 72: pressurizing chamber 74, 76: master cylinder
passage 100: pressure increasing mechanism 104: stepped piston 110:
large diameter chamber 112: small diameter chamber 132:
high-pressure-side check valve 138: manual-side check valve 134:
mechanical pressure-increasing device 150: individual passage 152:
common passage 153: pressure holding valve 156: pressure reducing
valve 170: controlled-pressure passage 172: pressure-increasing
linear control valve 176: pressure-reducing linear control valve
178: output hydraulic-pressure control valve device 190: servo
pressure passage 192: pressure increasing mechanism cut-off valve
218: brake switch 220: stroke sensor 222: master-cylinder pressure
sensor 224: accumulator pressure sensor 226: brake-cylinder
pressure sensor 228: level warning 230: wheel velocity sensor
* * * * *